What the other two guys said.
Plus, it's important to remember to play to the best of your abilities on the field, to try to glorify God in what you do, no matter how unimportant it may seem in the greater scheme of things.
I don't think it's right to pray for a team's success. But I think it's fine to pray that the team members play to the best of their abilities, and that their play transcends the here and now to show the glory of God, however dimly it may be reflected, just like in any human endeavour. I think it's fine to pray that what happens on the field exemplifies the best qualities of sportsmanship.
God does not care about which team wins. God is with everyone. Of course, I suppose that just like with anything else, God could use a sports team to impart a message. Why not?