Interleague play

Early discussions

Regular season interleague play was discussed for baseball's major leagues as early as 1903, when the two major leagues made peace and formed the National Commission as governing body. The first National Commission Chairman, Cincinnati President Augustus Hermmann, who had already been a proponent of interleague play, proposed an ambitious scheme in late-1904. His plan would've seen the two leagues' ending their seasons earlier, after approximately 116 games, "and then have every National League team play two games in every American League city, and have every American League team play two games in every National League city." Another interleague play idea was floated around the same time by Boston Americans owner John Taylor, whose plan was for each league to play its full 154-game schedule, to be followed by not just a championship series between the two league winners, but also by series' between the two second-place finishers, the two third-place teams, and all other corresponding finishers.

In August 1933, several owners reacted favorably to a proposal by Cubs' President William L. Veeck to have teams play four interleague games in the middle of the season, beginning in 1934. In December 1956, Major League owners considered a proposal by Cleveland general manager and minority-owner Hank Greenberg to implement limited interleague play beginning in 1958. Under Greenberg's proposal, each team would continue to play a 154-game season, with 126 within that team's league, and 28 against the eight clubs in the other league. The interleague games would be played immediately following the All-Star Game. Notably, under Greenberg's proposal, all results would count in regular season game standings and league statistics. While this proposal was not adopted, the current system shares many elements. Bill Veeck predicted in 1963 that Major League Baseball would someday have interleague play. While the concept was again considered in the 1970s, it was not implemented until the 1990s, at least in part as an effort to renew the public's interest in MLB following the 1994 players' strike.

Interleague play introduced

MLB's first regular season interleague game took place on June 12, 1997, as the Texas Rangers hosted the San Francisco Giants at The Ballpark in Arlington. There were four interleague games on the schedule that night, but the other three were played on the West Coast, so the Giants–Rangers matchup started a few hours earlier than the others. Texas' Darren Oliver threw the game's first pitch and San Francisco outfielder Glenallen Hill was the first designated hitter used in a regular-season game by a National League team. San Francisco's Darryl Hamilton got the first base hit in interleague play, while Stan Javier hit the first home run, leading the Giants to a 4–3 victory over the Rangers.

From 1997 to 2001, teams from the American League West played teams from the National League West, teams from the American League Central played teams from the National League Central, and so on, typically scheduled to alternate between home and away in consecutive years. However, in 2002, the league began alternating which divisions played which divisions, and thus in 2002 the American League East played the National League West, the American League Central played the National League East, and the American League West played the National League Central. Matchups which had been of particular interest prior to this format — mainly geographic rivals — were preserved. This is expected to be the continuing format of the interleague schedule. Corresponding divisions were skipped once when this rotation began, but were put back in the rotation in 2006.

From 2002 to 2012, all interleague games were played prior to the All-Star Game (with the exception of games postponed by weather that were made up after the All-Star Game). Most games were played in June and early July, although beginning in 2005, interleague games were played during one weekend in mid-May.

The designated hitter (DH) rule is applied in the same manner as in the World Series (and the All-Star Game prior to 2010). In an American League ballpark, both teams have the option to use a DH. In a National League ballpark, both teams' pitchers must bat. Some baseball observers feel it might be of better interest to reverse this (in other words, always follow the DH rule of the visiting team instead of the home team). This would expose the fans of the home team to the other league's rules. Fans of AL teams could see the strategy involved in having the pitchers bat, while fans of NL teams could see career-designated hitters such as Travis Hafner bat more than once a game in a pinch-hitting role. Teams from both leagues have both benefited and have been at a disadvantage when it comes to the DH rule in interleague play. For instance, Barry Bonds, who spent his entire career in the National League and actually won eight Gold Gloves earlier in his career, was used strictly as a DH later in his career when the San Francisco Giants played away interleague games due to his poor fielding. Conversely, Boston Red Sox slugger David Ortiz, who spent his entire career in the American League and was the Red Sox's regular DH, was forced to play first base when the Red Sox had away interleague games, forcing the Sox to give up good defensive fielding in favor of retaining Ortiz's power hitting.

After the 2010 interleague play, the American League holds an all-time series advantage of 1,808–1,652 and has finished with the better record in interleague play for 7 straight seasons, dating back to 2004. 2006 was the most lopsided season in interleague history, with American League teams posting a 154–98 record against their National League counterparts. The team with the best all-time record in interleague play is the New York Yankees of the AL at 144–102 (.585), followed by the Chicago White Sox at 143–104 (.579). The Miami Marlins holds the NL's best interleague record at 127–107 (.543), followed by the St. Louis Cardinals at 109–96 (.532).

In 2007, two teams — the Los Angeles Dodgers and the Baltimore Orioles — played six games with more than one interleague opponent. The Dodgers played both the Toronto Blue Jays and the Los Angeles Angels of Anaheim while the Orioles played both the Arizona Diamondbacks and the Washington Nationals. This happened again in 2012 as the New York Yankees played both the New York Mets and the Atlanta Braves for six games. The Miami Marlins also did this, playing both the Tampa Bay Rays and Boston Red Sox for six games each.

The first Civil Rights Game was an exhibition interleague game between the Cleveland Indians and St. Louis Cardinals in AutoZone Park on March 31, 2007. The first regular season Civil Rights Game was an interleague game between the Chicago White Sox and Cincinnati Reds in Great American Ball Park on June 20, 2009.

Since the introduction of interleague play, two teams have shifted leagues: the Milwaukee Brewers from the American League to the National League in 1998, and the Houston Astros from the National League to the American League in 2013. As a result, a 2013 interleague series between the two teams made it the first time that two teams faced each other in an interleague series after both teams previously faced each other in an interleague series representing opposite leagues: the two teams met from September 1–3, 1997 (Houston in NL, Milwaukee in AL), then again from June 18–20, 2013 (Houston in AL, Milwaukee in NL). In both instances, the series took place in Houston, with the team representing the American League winning 2-1. From 1998 to 2012, both teams were division opponents in the National League Central.

Interleague statistics

The following is the text of Major League Baseball's policy regarding the compilation of statistics as a result of Interleague Play:

"For the first time in the history of Major League Baseball, Interleague games are to be played during the regular season. Breaking tradition always brings about controversy and the matter of baseball records is no exception."

"It is the opinion of Major League Baseball that there is no justification for compiling a new volume of records based on Interleague Play. On the contrary, the sovereignty of each league's records will be retained, and if a player or a team breaks a record against an Interleague opponent it will be considered a record in that league. In cases where two teams – as Interleague opponents – break a league or Major League record, that record will be annotated with the phrase 'Interleague game.' Streaks by both teams and individual will continue (or be halted) when playing Interleague opponents in the same manner as if playing against an intraleague opponent. In essence, records will be defined by who made them rather than against whom they were made."

"The official statistics of both leagues will be kept separately as they have in the past. This means statistics for each team and their individual players will reflect their performance in games within the league and also in Interleague games without differentiation."

Interleague-play leaders

A list of leaders in the following categories is available on the MLB.com website.

Batting average (min. 300 at-bats)

Hits

Home Runs

Runs Batted In

Wins (by pitcher)

ERA (min. 100 innings)

Saves

Year-by-year Stats

Geographical matchups and natural rivals

Certain interleague matchups are highly anticipated each year, due to the geographic proximity of the teams involved. Many cities, metropolitan areas and states contain at least one team in each league. In of each of these "rivalry" matchups, the two teams meet annually for four games, two in each ballpark. Prior to 2013, there were six games between the two teams, three per ballpark:

Baltimore Orioles v. Washington Nationals — Beltway Series, Parkway Series or MARC Madness

Chicago Cubs v. Chicago White Sox — Windy City Series, Crosstown Classic or Red Line Series. The two teams played in the 1906 World Series.

Cincinnati Reds v. Cleveland Indians — Ohio Cup

Detroit Tigers v. Pittsburgh Pirates — While this series only became a rivalry because the other AL and NL Central teams were already paired up, it has become popular with fans of both teams, possibly due to the rivalry between the NHL's Detroit Red Wings and Pittsburgh Penguins. The two teams have several other connections as well. The Tigers' AA Minor League affiliate, the Erie SeaWolves, is located near Pittsburgh, is a former affiliate of the Buccos, and has retained the logo of a wolf wearing a pirate bandanna and eye patch. Additionally, Jim Leyland, former manager of both the Pirates (1986–1996) and the Tigers (2005–2013), remains popular in Pittsburgh where he continues to reside. The two teams played in the 1909 World Series.

Kansas City Royals v. St. Louis Cardinals — I-70 Series or Show-Me Series, and named so because the cities of Kansas City and St. Louis are both in Missouri, and connected by Interstate 70. The two teams played in the 1985 World Series.

Los Angeles Angels of Anaheim v. Los Angeles Dodgers — Freeway Series

Miami Marlins v. Tampa Bay Rays — Citrus Series

Milwaukee Brewers v. Minnesota Twins — The Twins and the Brewers were formerly regional rivals in the American League. The two metro areas are connected by Interstate 94. However, the term "I-94 Series" is used almost exclusively to refer to the games played between the Milwaukee Brewers and the Chicago Cubs, and interleague contests with the also-former rival Chicago White Sox.

New York Mets v. New York Yankees — Subway Series The two teams played in the 2000 World Series.

Oakland Athletics v. San Francisco Giants — Bay Bridge Series or Battle of the Bay. The two teams played in the 1989 World Series as well as the 1905 World Series, 1911 World Series, and 1913 World Series when they were located in Philadelphia and New York, respectively.

Arizona Diamondbacks v. Houston Astros — This interleague rivalry was introduced in 2015, replacing the San Diego Padres v. Seattle Mariners rivalry.

In 2014, the five AL teams that qualified for the postseason (Angels, Athletics, Orioles, Royals, and Tigers) all had geographical rivals among the five NL teams who qualified for the postseason (Dodgers, Giants, Nationals, Cardinals, and Pirates, respectively).

Split rivalries

Four teams in the East and West form a "split rivalry" where the rivalry pairings alternate in odd- and even-numbered years.

In the East:

Odd-numbered years:

Boston Red Sox v. Philadelphia Phillies

Toronto Blue Jays v. Atlanta Braves

Even-numbered years:

Boston Red Sox v. Atlanta Braves

Toronto Blue Jays v. Philadelphia Phillies

In the West:

Odd-numbered years:

Seattle Mariners v. Colorado Rockies

Texas Rangers v. San Diego Padres

Even-numbered years:

Seattle Mariners v. San Diego Padres

Texas Rangers v. Colorado Rockies

Former interleague rivalries

Baltimore Orioles v. Philadelphia Phillies – Ended in 2006, when the Washington Nationals replaced the Phillies as the Orioles' rival. Although the Nationals moved to Washington in 2005, the schedule for that season was already established, so the Washington-Baltimore rivalry series could not start until the next season.

Houston Astros v. Texas Rangers (Lone Star Series) Ended in 2013, when the Astros moved to the American League West. The two teams now play each other 19 times a year as divisional rivals.

Montreal Expos v. Toronto Blue Jays (Pearson Cup or The All-Canadian Series) Ended in 2005, when the Expos moved to Washington, D.C. The 2005 schedule was already set before the Expos left Montreal, so the Nationals played a series with the Blue Jays that season.

Scheduling

In the American League, each team used to play 18 interleague games a year, but because the National League had two more teams than the American, only four NL teams would play a full 18-game interleague schedule, with the remaining twelve teams playing only 15. With the exception of the two NL teams playing each other, all teams were involved in interleague play at the same time (originally in June and July), playing only interleague opponents until the interleague schedule was complete for the year. The schedule was later changed to occur only in June; in 2005, it was changed again to allow for more weekend interleague games, with each team playing one series during the third weekend in May and the rest in mid-to-late June (occasionally stretching into early July).

On April 1, 2013, for the first time in major league baseball history, an interleague game was played on Opening Day, between the Los Angeles Angels of Anaheim and the Cincinnati Reds at Great American Ball Park, with the Angels claiming the distinction of winning that game 3-1 in 13 innings. The Reds, however, would win the next two contests by scores of 5-4. Also, on September 29, 2013, for the first time in major league baseball history, an interleague game was played on the last day of the regular season, between the Miami Marlins and the Detroit Tigers at Marlins Park. The Marlins not only claimed the distinction of winning that game 1-0 in walk-off fashion, but also saw their pitcher Henderson Álvarez pitch a no-hitter, marking just the 7th time a no-hitter was tossed in an interleague contest (including Seattle's combined no-hitter versus the Dodgers in 2012). With the win, the Marlins earned the sweep.

As of 2012, every major league team has had at least one interleague series with each team in the opposing league. Additionally, every major league team has at least one victory with each team in the opposing league; the Pittsburgh Pirates 5-0 victory over the Oakland Athletics on July 10, 2013 marked the first time the Pirates defeated the A's. Entering the game, A's-Pirates was the only interleague series (and subsequently, the only MLB series overall) that one team won every game.

Every team has also hosted and visited every other team at least once. On July 25–27, 2016, the San Diego Padres made their first ever trip to Toronto, with the Blue Jays winning two out of three games. The two teams had previously played in San Diego in 2004, 2010, and 2013.

Effect of Astros joining AL on scheduling

In 2013, the Houston Astros joined the American League, giving each league 15 teams and thereby necessitating that interleague games be played throughout the season, including on Opening Day and during key division races all the way to the end of the season. This did not require expanding the total number of interleague games, because the probability of an interleague game during the Astros in the NL era was 252/2430 or about 1 in 9.6 games (this number is not an integer because not all teams had the same number of interleague games). With an odd number of teams in each league, one team in each league would be the "odd man out" and have to play an interleague game to fill out the schedule, meaning as few as 1 in 15 games could be interleague (14 AL teams in 7 AL games, 14 NL teams in 7 NL games and 1 AL and 1 NL team in an interleague game). Despite this, there have been proposals to increase interleague play to 30 games. While the increase to 30 games is highly unlikely for the foreseeable future, a smaller increase took place immediately, having every team to play 20 interleague games.

Since the 2013 season, the 20 interleague games are played in eight series. Each team plays one three-game series against four teams from one division in the other league, and two two-game series (one home, one away) against the remaining team in that division. Since 2002, this has been on a rotating basis. The remaining four games are played against a team's "natural rival" in two back-to-back two-game series. Should a team's natural rival be a member of the division they are scheduled to play as part of the yearly rotation (this first occurred for all teams in 2015), the team will play home-and-home three game series against the natural rival, home-and-home two game series against two other opponents (one of which takes place back-to-back within the same week), and single three game series against the last two (one home, one away). For 2013, the natural rivalry games were played from May 27–30. Teams played in one city on May 27 and 28, then traveled to the other city for games on May 29 and 30. This dynamic was repeated from June 15–18, 2015, except that no pairs of natural rivals played each other during this time. For 2014, however, these natural rivalry games were spread out over the season, between early May and early August. They were spread out even further in 2016, ranging from the second week of the season in April through late August. Because of the requirement of near daily interleague play (the only exception being if not all teams are playing) spreading out interleague play throughout the year, not every team will be in interleague play on the same day.

Most days, there will be either one or three interleague games as the average number of interleague games per day will be 1.68 [(20 interleague games per team x 30 teams in MLB)/(179 total days in baseball season (including off days and excluding the All-Star break))/2 teams per game]. With 15 teams in each league, the number of interleague games is almost always odd, with exceptions based on when teams from each of the AL and NL have the same off day. Doubleheaders and make-up games also apply should a rainout or other extended delay requires a game (or games) to be postponed.

Arguments

Since its introduction, regular-season interleague play has continued to be a source of controversy among baseball fans and others involved with the sport. Among the arguments used in favor of and in opposition to interleague play are the following:

Pros

Interleague matchplay increases attendance; however, these numbers may be skewed, as interleague games are primarily played on weekends, when attendance is higher across the board, and in June, when school is not in session and temperatures are higher than some of the other months of the season.

Season-long interleague play should remove the statistical issue of having every interleague game during months when school is not in session.

Fans can see players they might not otherwise get to see, especially those who have only ever played in one league.

Certain geographic rivalries are played out during the regular season that otherwise might not happen for years at a time. The Yankees now play four games against the Mets each season whereas they would only have gone head to head in the 2000 World Series if not for interleague play. From 1962 until interleague play, the Mets and the Yankees played each other in a single game, the annual Mayor's Trophy Game, which was an exhibition game even though it was played during the regular season.

It creates matchups that might not have been seen in generations. For example:

During the 2004 season, the Giants and Red Sox played each other for the first time since meeting in the 1912 World Series.

The Red Sox had never played at Wrigley Field (an NL park since 1916) until 2005.

In 2004, the Yankees and Dodgers met for the first time since the 1981 World Series at Dodger Stadium.

In 2008, the New York Yankees visited the Pittsburgh Pirates for the first time since the 1960 World Series.

In 2011, the Chicago Cubs traveled to Fenway Park for a series with the Boston Red Sox in what was the Cubs' first visit to the ballpark since the 1918 World Series.

It allows for a rematch of the previous World Series. This has occurred in ten of the twenty seasons of interleague play. In 2000 (1999 World Series, New York Yankees at Atlanta Braves), 2001 (2000 World Series, New York Mets at New York Yankees), 2002 (2001 World Series, Arizona Diamondbacks at New York Yankees), 2005 (2004 World Series, Boston Red Sox at St. Louis Cardinals), 2006 (2005 World Series, Houston Astros at Chicago White Sox), 2007 (2006 World Series, St. Louis Cardinals at Detroit Tigers), 2009 (2008 World Series, Philadelphia Phillies at Tampa Bay Rays), 2010 (2009 World Series, Philadelphia Phillies at New York Yankees), in 2014 (2013 World Series, Boston Red Sox at St. Louis Cardinals), and in 2016 (2015 World Series, home-and-home between New York Mets and Kansas City Royals).

It allows the relative strength of the two leagues to be measured against each other over 300 games per year, rather than just in the World Series once per year.

Cons

Most American League pitchers do not like taking batting practice for the opportunity to bat in one or two games (unless they've played in the National League before). These pitchers are also unaccustomed to running the bases, which can lead to injury and premature fatigue. (For example, Chien-Ming Wang suffered a season-ending lisfranc sprain on his right foot when running the bases during a Yankees–Astros game at Minute Maid Park on June 15, 2008.)

The World Series and All-Star Game are robbed of the mystique that used to result from the two leagues playing completely exclusive schedules during the regular season: in the case of the World Series, the "best in the American League" playing the "best in the National League" for the only time that season.

More games against interleague opponents means fewer games against same-league and division rivals – the latter of which may be more compelling. However, the leagues currently play an unbalanced schedule that favors divisional opponents rather than teams from other divisions (which is important due to the postseason qualifying structure – only the best team from a given division is guaranteed a berth in the postseason). Now, each divisional opponent meets each other 19 times as opposed to 18 in previous years, and each natural rivalry sees only 4 games as opposed to 6 in previous years.

Some have argued that the AL possesses an unfair advantage over the NL because of the designated hitter rule in the AL. When NL teams are on the road, they are forced to find a DH in place of their pitcher, who would normally bat ninth. Sometimes, the NL team will use one of their star hitters as the DH and use a bench player to fill in for the appointed DH, and other times, the NL team will simply use a bench player as the DH and have him bat later. In either case, however, the benefits of using a DH in place of the pitcher are minimal, especially considering that the AL designated hitters have seen more action in their positions and that AL teams still possess their full 9-man batting lineup. Even when the NL team is hosting, arguments have been made that there is no real benefit for the NL team either. For the most part, designated hitters are also good fielders, meaning that they can still be used in the game. And although AL pitchers see less action than NL pitchers, stats have showed that AL pitcher batting average is not much lower than NL pitcher batting average, in large part due to the fact that several AL pitchers have played in the NL. For these reasons, some have argued that the NL should adopt the DH, while others have argued that the AL should drop the DH.

These cons apply primarily to the 1997–2001 and/or 2002–2012 formats and not necessarily to the current format:

The "rivalry" series that consist of six games a year for some teams leads to further scheduling inequities. For example, the New York Yankees play the recently poor New York Mets six times a year, while their division rival Baltimore Orioles must play the recently strong Washington Nationals six times a year.

Some teams play a certain opposite-league team more than a certain same-league team. For example, the San Diego Padres played the Seattle Mariners (an American League team) six times during the 2012 season. However, the Padres only played the Washington Nationals (a National League team) 5 times in the 2012 season.

Most notably, teams no longer play identical opponents as their divisional rivals, and even where they do, they don't always play them an identical number of times. This can lead to "strength of schedule" disparities like those the NFL has to deal with on a yearly basis. For example, in any given season, one NL Central team might play every AL East team except the (strong) first place team, while another NL Central team plays all but the (weak) last place team.

In the current format these inequities are sharply reduced, since all teams within a division will have the same opponents from the rotating division each season, while the rivalry series is reduced to four games each season.

This issue is not completely alleviated with the Rangers/Astros vs Rockies/Dbacks split rivalry in the western divisions, as one of the Texas teams will get 4 games against the cellar-dwelling Rockies and the other has to face the division-contending Dbacks. This can play a factor in a tight AL West divisional race, which the Rangers won by 2 games over the Astros in 2015.