Him being cleared on Thursday , implies he only had 2 practices in the last 3 weeks.
To claim that without the broken hand ou would have won is silly. It's also silly to say with any certainty that Texas would have still won had he not had the injury.
What we do know is that the ou staff played Mateer because they believed that he gave them the best chance to win, and that they lost.
Injuries are a part of the game, and ideally you have enough depth to handle injuries without too much impact. To speculate about how this or any game would have gone, without injuries seems pointless to me.