[staticassertion]

Even if you hadn't lost any muscle mass, zero chance you're going to see the same exercise performance on a calorie deficit.

[throwaway2037]

This is untrue. There are 100s of YouTube videos of amateur body builders preparing for a show. They are able to maintain their muscle mass while in a calorie deficit. Yes, it is insanely hard, but it can be done.

[staticassertion]

I didn't say that you can't maintain muscle mass. I'm saying your performance will suffer.