I'm not sure that he's even GOT an injury. His play was crap, the baggage he brought is nothing but a distraction, and there's no reason to believe either situation is going to improve.
I'd think it more likely that they just want to pay him to leave, and disassociate himself with the browns.
Ain't nobody faking a torn achilles. He's out for the season. If somehow the team and NFL found out he faked this injury, they could decide not to pay him the rest of this season.
Guaranteed contracts are guaranteed as long as he doesn't retire or up and quit, which this would qualify.