Whatever power he normally has isn't working. He's not much for keeping himself unhurt, apparently, without it. Ergo, he needs to stay safe, and let Whisper handle this nasty customer herself.

In a wide open space, it'd be easy to outmaneuver the crab and take potshots at it, but here she's gotta be a bit more thoughtful - or a lot smashier. When it lunges, she winds up and bashes the pincer away, leaving more cracks, before using the opening and her momentum to wind up for an even bigger swing right in its big crabby face.