<!–start image–><!– end image–>Regret can be a poison, sneaking into the system and overtaking any other rational emotions or thoughts. And it’d be plausible to think USC quarterback Mitch Mustain is battling a pretty severe case of regret. Whether or not the decision to come to USC in the first place and the subsequent decision to stay are eating him up on the inside now, if things don’t change for the talented QB, he’ll be asking himself “What if