Mike is reeling from Raphael's accusations, rather than by his brute force.
Shredder almost won Leonardo over with a sword?
And then there's the injury, the one that no one ever talks about, and how Raph is using that previous hurt in the present. When Leo's leg begins to give way, Mike steps forward once again. This time though, he doesn't reach for either cousin.

"Raphael, that's enough!"