Don't go out of your way to offend. You won't change their minds because they are closed. I try to remember that for them, it might be the only way they can handle life. Take the high road and if they give you the hairy eyeball, just smile back at them. Lead by example. Be tolerant but remain true to yourself. You have the courage to think independently. You are to be congratulated for that.
When I was younger and had something to loose, I played the game a bit. Now that I am older, I look around and guess what, lots of times there are others like me, smirking and just enjoying the show.
Just tell them YOU worked hard to become an allstar football player, and god didn't do shit, then excuse yourself by throwing 600 yards and 4 TD passes! and try not to let this happen to you...
Well it doesn't help that a good 90% of the US, where I suspect you are, are Christian/Catholic. They've probably never met an atheist or even know that we exist, though the later option would be born of pure ignorance. So it's not out of disrespect, they just didn't think that there may be someone who disagrees with their beliefs. After all it may be that they've only know others of the same faith for their whole lives. I've actually met a couple of people like that here where I live. Their amazement at finding out I'm atheist was actually really amusing. The evil eye is the same thing and you really shouldn't let it bother you. Maybe you should give the evil eye back just for the fun of it.
The best you can do is keep your language as secular as possible when the holidays/family gatherings come around. Hint that you don't agree but don't bring it up yourself and if they ask, answer honestly. If they try to convert you, state your reasons for being atheist and walk away.
Your response should depend on the context. Is the goodwill of these people important to you? Is their ill will dangerous? How important is that football spot to you? Are you willing to make a stand over it?
I'd say look at the people around you. If it's a friend you can talk to about it, you can politely decline to pray and point out the error of their assumption. If you're willing to risk your place on the team, you can stand while everyone is praying and denounce it as an abuse of the First Amendment. (Public school, yes?) If it's a family dinner and you don't want to offend granny, just quietly bow your head and plan the quickest way to grab a turkey leg before Uncle Joe & the dog get them.