On Wednesday, Football Outsiders begins its "Plugging the Holes" series, in which it will target the offseason issues facing each team in the NFL by division. Bill Barnwell begins with the AFC West.

Denver Broncos: What went wrong in the second half?
The Broncos' 2-8 collapse after a 6-0 start cost them what appeared to be a guaranteed playoff spot; teams that start 6-0 have historically made the playoffs more than 96 percent of the time. The 2003 Vikings were the only team since 1990 to also start 6-0 and proceed to miss the playoffs. So what changed? And what do the Broncos need to do in 2010 to play more like their first-half version?