The 1999 Denver Broncos season was the team's 40th year in professional football and its 30th with the National Football League (NFL). After winning its second consecutive Super Bowl with a win over the Atlanta Falcons in Super Bowl XXXIII in Miami, the team suffered the retirement of Super Bowl XXXIII MVP quarterback John Elway during the off-season. Elway had spent his entire career with the Denver Broncos, and much of the focus in the weeks leading up to the season centered on the void left by Elway's departure. Head Coach Mike Shanahan announced that third-round 1998 draft pick Brian Griese, son of Miami Dolphins Quarterback Bob Griese, would take the reins of the offense, passing over veteran and credible back-up QB Bubby Brister.
In the preseason, the Broncos played in the first and so far only NFL game held in Australia. On August 7, 1999, before a crowd of 73,811 spectators at Stadium Australia in Sydney, the Broncos defeated the San Diego Chargers 20–17.
Although no one expected a serious defense of their title, the Broncos would stumble out of the gate this season, losing the first four regular season games. Many of the games would be decided in the final two minutes of play, but the Broncos found themselves on the losing end at 6–10. It was their first losing season since 1994, the worst season since 1990 and the worst record of the five-team AFC West. This was the worst-ever season for a team defending their Super Bowl title.
Statistics site Football Outsiders calculates that the Broncos went from the league's 28th (third-easiest) schedule in 1998, to the hardest schedule in 1999.:
Before 2011, the worst one-year increase in strength of schedule belonged to the 1999 Broncos. Denver had ridden the third-easiest schedule (in a 30-team league) to a Lombardi Trophy in 1998, only to fall apart the next season under the weight of John Elway's retirement, Terrell Davis'[s] Week 4 injury, and – oh, by the way – the toughest schedule in the league.
This was the largest single-season change in Football Outsiders' rankings until the 2011 St. Louis Rams.
Week 4 saw star running back Terrell Davis, who was last year's league MVP, hurt his knee and was placed on injured reserve for the remainder of the season.