NFL Offseason - Usually, a trainwreck leads to injuries. In the NFL, however, injuries help lead to a trainwreck. That was certainly the case in Denver this season, as the Broncos led the NFL in Football Outsiders' adjusted games lost metric which measures injuries to starters and important situational players.
No, injuries do not explain the decline and fall of Russell Wilson, and they don't mitigate the strange coaching decisions of Nathaniel Hackett. But a Denver team with average health might have finished the year 7-10 instead of 5-12. That's a disappointing season, but not a disaster.