A professional athlete who has to be told multiple times to get in shape? I'm not sure that's a good fit right now.
Tougher for some guys than others. I'd have to dig up the article, but I vaguely remember something with Ryan Miller where he didn't want to bulk up too much since he'd be sacrificing flexibility. But then there are cases like Robin Lehner where it's just a guy just being overweight.
Your comment also reminded me of this Skip Bayless op-ed from years ago where he blamed the NFL for Maurice Clarett not panning out. The NFL didn't let Clarett enter the 2004 Draft after he got kicked off Ohio State's squad. While waiting for that extra year, Clarett got out of shape and had issues with drugs/alcohol. That was the NFL's fault according to Bayless. And that was point where I tuned out anything he ever has to say.