My buddy is a Dr. (PT, i always use the Hangover line "Yeah, but you're not a real doctor. You're just a PT"), he said it's basically up to how well he can drive with the brace. Lateral mobility and backpedaling shouldn't be an issue. It's the fact that he doesn't have control of his calf, and it's one of, if not the strongest muscle in the body (can't remember which he said).
Main issue is going to be driving on the ball, short passes etc. It's just impossible to tell how well he'd play with the brace. Obviously not nearly as well as he would without. This is the same guy that called Dez' injury to the week, even before it was "official". Haha, we watch games sometimes, and he saw the injury and then he just said it out loud without me even asking.
It's not exact obviously if you didn't do the original diagnosis, but he knows his stuff. He laughed when we made the pick, didn't think he'd ever play again, but he conceded that Dr. Cooper is a leader in the field and prob knows best.