That was one of the little things that the Fight Night series got right. Guys would bleed onto the floor of the ring, and it would stay there for the rest of the round, at which point it was presumably cleaned off-camera. It added a lot to the atmosphere of the game. (By the way, aside from Fight Night Champion, those games were rated T, just like WWE 2K16. I don't think 2K16 lacks mat blood because of the ESRB.)