Its Moon day. I think Moon would have beaten Tapia. Johnny, not enough power to deter Moon, and no defensive wiz. I think Moon mauls him and takes an 8-4ish decision.
In the UK, we call Moon Day night. And I completely agree. Moon wins a clear decision, wherein which there's some brilliant exchanges, but Moon's gritty skill and ridiculous workrate overwhelms Johnny. Tapia wouldn't fold, but I think he'd be comfortably outworked, and the power of Moon and relentlessness would probably mean Tapia's a bit dissuaded from throwing as much. It all goes to Moon winning. I actually think Moon vs Romero would be a better fight.
Johnny is really hard to predict in fantasy fights. I have a hard time seeing him lose to Moon, though.