I didn't see this posted anywhere, but apparently Spencer Larsen fell in the shower and hurt his shoulder
Linebacker Spencer Larsen, a sixth-round draft pick in 2008, reportedly slipped and fell on a wet spot on the floor. Larsen has a shoulder injury, and he'll miss a "few weeks."
The Associated Press surmises that Larsen suffered the injury less than 90 minutes before kickoff, because Larsen wasn't on the list of inactive players for the Week One game at Cincinnati.
Coach Josh McDaniels said that the injury wasn't the result of horseplay. (And since NFL head coaches always tell the truth, we believe it.)