As this recent rash of injuries has shown, you can never have too much goalie depth. Keep him and let him walk in July.
I imagine they'll try and ride a (hopefully healthy and fresh) Jimmy down the stretch, so I'd rather Mrazek go to GRs and play some games and try and help that team into the playoffs. Let Monster warm the bench.
Keep in mind 90% of this team's injuries in goal is Monster (yes, I pulled that number out of my ass as a joke... kind of).