Football Outsiders released their annual adjusted games lost article, where they use their database from the weekly NFL injury reports for every season 2001. Here is their explanation:
This allows us to measure not just who played and who didn’t, but who was able to play with injuries, even if those injuries meant the player was at something less than 100%. That’s why we call this metric adjusted games lost — in addition to players who missed games entirely, we also count those who hit the field after appearing on the injury report at an adjusted rate. Further, we track whether the injured player was a starter, a situational reserve, or simply bottom-of-the-roster fodder. Obviously, an injury to a starting tackle is more important than one to a guy who only plays on special teams.
The San Francisco 49ers were the fourth-most injury struck team in 2019 according to Football Outsiders, which was one spot worse than 2018:
It wasn’t as if the 49ers were hit on one side of the ball or the other. San Francisco lost the tenth most-games due to injury and the seventh-most on defense.
Looking at the list, and this is common sense, the teams with the fewest injuries generally had good seasons. The leaders in adjusted games loss on offense were Baltimore, who had the best offense in the league, and the Patriots, who had the best defense in the league per DVOA. The Vikings suffered the fewest injuries overall at 25.6. The curveball is that both Super Bowl teams finished below average. The 49ers had the third-most adjusted games lost at running back, and they were near the top for defensive line, linebacker, and defensive back. Further proof that the 49ers boast one of the deepest rosters in the NFL. More importantly, they have more talent among the starters.
You’d think 2020 the 49ers would finally catch a break from the injury bug, but San Francisco has been one of the ten most injured teams in the NFL every year for the past seven years according to adjusted games lost.