If youre a pro boxer.... you should know the rules. if you dont know them, then your manager or your trainer should know. either way, no. you can not fight mma on a suspension. the state athletic commission governs over all contact sports. do yourself a favor, take the 90 day rest. the time will fly by. the suspension is meant to protect you. You dont want to end up like Stephen Johnson. (if you dont know who he is, boxrec him.)