Don doesn't expect that, and he barely has time to guard his head before Raph is on him again.

The impact hits him square in the middle, and he's pretty sure he'd be suffering some serious internal injuries right now if he were human. As it is, he's definitely going to be hurting when this is over.

Why isn't it over? What's it even about at this point?

Don protects himself as best he can, and hopes Raph's rage will exhaust itself soon.