Could be FFX and the "almost unwinnable" battle is your first Blitzball match. Win or lose changes nothing in the overall story. You're supposed to get your ass kicked.

I handed the controller over to a friend who wanted to see if it was possible to win that fight (and he was good at Blitzball.) The answer is YES! a good BB player can win as long as they manually control the players (the computer is bad.) Your prize is a slightly different cutscene and some of the opposing team's BB players going free agent later in the game. That's it.