Shooting your load onto his face is a sure fire way to reinforce your role as alpha male, and show your opponent in his proper place as a cum rag for real men.  After all, he lost the match. 

Plus it’s fun to watch his humiliation as he walks back into the locker room, letting his teammates see your load coating his handsome, masculine face.  Wont be long, before his own teammates start cornering him in the showers or weight room and feeding him cock.  His days as a respected team leader and friend are over.