On base plus slugging

Equation

The basic equation is

O P S = O B P + S L G

where OBP is on-base percentage and SLG is slugging average. These averages are defined

S L G = T B A B

and

O B P = H + B B + H B P A B + B B + S F + H B P

where:

In one equation, OPS can be represented as:

O P S = A B ∗ ( H + B B + H B P ) + T B ∗ ( A B + B B + S F + H B P ) A B ∗ ( A B + B B + S F + H B P )

Interpretation of OPS

OPS does not present a complete picture of a player's offensive contributions. OPS does not consider such factors as baserunning, basestealing, and the leverage/timeliness of performance.

More expansive sabermetric measurements do attempt to incorporate some or all of the abovementioned factors. Nonetheless, even though it does not include them, OPS correlates quite well with team run scoring.

Other sabermetric stats, such as runs created and Wins Above Replacement, attempt to express a player's contribution directly in terms of runs and/or wins. However, a player's OPS does not have a simple intrinsic meaning.

OPS is a convenient but controversial measurement. OPS weighs on-base percentage and slugging average equally. However, on-base percentage correlates better with scoring runs. Statistics such as wOBA build on this distinction using linear weights. Additionally, the components of OPS are not typically equal (league-average slugging percentages are usually 75-100 points higher than league-average on-base percentages). As a point of reference, the OPS for all of Major League Baseball in 2008 was .749.

An OPS scale

Bill James, in his essay titled "The 96 Families of Hitters" uses seven different categories for classification by OPS:

This effectively transforms OPS into a 7-point ordinal scale. Substituting quality labels such as Excellent (A), Very Good (B), Good (C), Average (D), Fair (E), Poor (F) and Very Poor (G) for the A-G categories creates a subjective reference for OPS values.

History

On-base plus slugging was first popularized in 1984 by John Thorn and Pete Palmer's book, The Hidden Game of Baseball. The New York Times then began carrying the leaders in this statistic in its weekly "By the Numbers" box, a feature that continued for four years. Baseball journalist Peter Gammons used and evangelized the statistic, and other writers and broadcasters picked it up. The popularity of OPS gradually spread, and by 2004 it began appearing on Topps baseball cards.

OPS was formerly sometimes known as "Production." For instance, in early versions of Thorn's Total Baseball encyclopedia, and in the Strat-O-Matic computer baseball game. This term has fallen out of use.

Leaders

The top ten Major League Baseball players in lifetime OPS, with at least 3,000 plate appearances through the end of the 2015 season, are (active players in bold):

1. Babe Ruth, 1.1636
2. Ted Williams, 1.1155
3. Lou Gehrig, 1.0798
4. Barry Bonds, 1.0512
5. Jimmie Foxx, 1.0376
6. Hank Greenberg, 1.0169
7. Rogers Hornsby, 1.0103
8. Manny Ramírez, 0.9960
9. Mark McGwire, 0.9823
10. Mickey Mantle, 0.9773

The top four were all left-handed batters. Jimmie Foxx has the highest career OPS for a right-handed batter.

Source: Baseball-Reference.com - Career Leaders & Records for OPS

The top ten single-season performances in MLB are (all left-handed hitters):

1. Barry Bonds, 1.4217 (2004)
2. Barry Bonds, 1.3807 (2002)
3. Babe Ruth, 1.3791 (1920)
4. Barry Bonds, 1.3785 (2001)
5. Babe Ruth, 1.3586 (1921)
6. Babe Ruth, 1.3089 (1923)
7. Ted Williams, 1.2875 (1941)
8. Barry Bonds, 1.2778 (2003)
9. Babe Ruth, 1.2582 (1927)
10. Ted Williams, 1.2566 (1957)

The highest single-season mark for a right-handed hitter was 1.2449 by Rogers Hornsby in 1925, 13th on the all-time list. Since 1925, the highest single-season OPS for a right-hander is 1.2224 by Mark McGwire in 1998, which was 16th all-time.

Source: Baseball-Reference.com - Single-Season Records for OPS

Adjusted OPS (OPS+)

OPS+, Adjusted OPS, is a closely related statistic. OPS+ is OPS adjusted for the park and the league in which the player played, but not for fielding position. An OPS+ of 100 is defined to be the league average. An OPS+ of 150 or more is excellent and 125 very good, while an OPS+ of 75 or below is poor.

The basic equation for OPS+ is

O P S + = 100 ∗ ( O B P ∗ l g O B P + S L G ∗ l g S L G − 1 )

where *lgOBP is the park adjusted OBP of the league (not counting pitchers hitting) and *lgSLG is the park adjusted SLG of the league.

A common misconception is that OPS+ closely matches the ratio of a player's OPS to that of the league. In fact, due to the additive nature of the two components in OPS+, a player with an OBP and SLG both 50% better than league average in those metrics will have an OPS+ of 200 (twice the league average OPS+) while still having an OPS that is only 50% better than the average OPS of the league. It would be a better (although not exact) approximation to say that a player with an OPS+ of 150 produces 50% more runs, in a given set of plate appearances, as a player with an OPS+ of 100.

Leaders in OPS+

Through the end of the 2015 season, the career leaders in OPS+ (minimum 3,000 plate appearances) were

  1. Babe Ruth, 206
  2. Ted Williams, 190
  3. Barry Bonds, 181
  4. Lou Gehrig, 178
  5. Rogers Hornsby, 175
  6. Mickey Mantle, 172
  7. Dan Brouthers, 170
  8. Joe Jackson, 169
  9. Ty Cobb, 168
 10. Pete Browning, Jimmie Foxx & Mark McGwire, 163

Source: Baseball-Reference.com - Career Leaders & Records for Adjusted OPS+.

The only purely right-handed batters to appear on this list are Hornsby, Foxx, and McGwire. Mantle is the only switch-hitter in the group.

The highest single-season performances were:

1. Barry Bonds, 268 (2002)
2. Barry Bonds, 263 (2004)
3. Barry Bonds, 259 (2001)
4. Fred Dunlap, 258 (1884) *
5. Babe Ruth, 256 (1920)
6. Babe Ruth, 239 (1921)
7. Babe Ruth, 239 (1923)
8. Ted Williams, 235 (1941)
9. Ted Williams, 233 (1957)
10. Ross Barnes, 231 (1876) **
11. Barry Bonds, 231 (2003)

Source: Baseball-Reference.com - Single-Season Leaders & Records for Adjusted OPS+

* - Fred Dunlap's historic 1884 season came in the Union Association, which some baseball experts consider not to be a true major league

** - Ross Barnes may have been aided by a rule that made a bunt fair if it first rolled in fair territory. He did not play nearly so well when this rule was removed, although injuries may have been mostly to blame, as his fielding statistics similarly declined.

If Dunlap's and Barnes' seasons were to be eliminated from the list, two other Ruth seasons (1926 and 1927) would be on the list. This would also eliminate the only right-handed batter in the list, Barnes.