It's impossible to tell if it's a lack of conditioning or the lack of recovery. Everyone should be in great shape right now after playing so many games.
I would think muscle imbalances would be identified in the offseason and addressed. It's a very explosive game. We're talking going all out 100% output. There's a certain amount of recovery that goes into and everyone recovers differently. The older you are the slower that process is.
I will be shocked if they make it through 3 games in 11 days without a bunch of issues. That's crap for recovery time between games. Which will lead to more injuries.
I believe the Chiefs are playing 3 games in 11 days as well, I just saw them bitching about it the other day.
Whomever made that schedule is an asshat.