He realized that the "real one was not with them" when one of the Pein's bodies ran head into his shield and was killed. At that point, he also came to the realization that he would not just be able to get up and run away. But I dispute that theory due to the revalation of reverse summoning.

I love this debate and both sides have great points. I actually see the logic that both sides are following. Great debaters on both sides.