This brings up another good question. I can see the OP happening in a sub-varsity game. If the coach said something before the game, that he might have two players in the game with the same number, do you cut him some slack knowing it's a sub-varsity game?

We did it a few years ago, informing the opposing coach of the situation before the game of course. The opposing coach had no problem with it at the time, but at halftime, he started griping about it causing problems for his players. My white hat said this is a freaking Saturday morning freshman game, give it a break.