ESPN Polled 51 NFL players and the majority of them (86%) says they wouldn’t have a problem with a gay teammate.
While there will always be a few players who don’t like it, in general I don’t think most would care. Once they know the boundaries, everything will be fine.
Locker rooms are often divided into little cliques anyway be it religious, racial and etc, so the people who are cool with it, will embrace a gay player and the ones who don’t just won’t deal with him off the field.
Plus most teams have a gay player on their roster, just isn’t public, but everyone knows. I know of several gay NFL players, not rumors, 100% facts, so it isn’t like most locker rooms aren’t use to it.