SERIOUSLY, this sounds JUST LIKE a guy I dated in college!! (I know it's not the same person, though, because the guy I dated didn't play football
.) He was very attractive, got plenty of attention from the ladies, but ALWAYS found some nonsense reason to break things off with women...
something about not wanting to date a girl unless he was sure she was the "one". In my case performance and size weren't the issues, emotional baggage was. Based on what you say above,
I think fearing impotency is jumping the gun a bit. I wouldn't be surprised if he has an insecurity, but I'd guess that it had more to do with him not wanting to get caught up in drama or not trusting his own judgement than anything else.
Men with commitment or confidence issues can avoid the HECK out of women.