I'd see what we could get for Patton this winter and allow Matusz, Britton, Pettit, Belfiore, and Chris Jones
to fight it out for the two LH bullpen spots next spring.
Any reason why you would dangle Patton over Matusz? They are both arbitration eligible after this year, and his the open market after the 2016 season, so controllable years isn't a problem. But Matusz has more trade value. He is having the slightly better season, and some teams might think there is a chance to convert him back to a starter. Plus, they will both get a raise this winter, but Matusz seems to get a higher raise because of the slightly better season, on top of the fact that he was already twice as expensive in the first place.
That being said, I wouldn't trade either. Although starters, Britton and Pettit are struggling in the minors. Jones and Belfiore have pretty ERA's, but horrid WHIP's. Maybe it will be better to have them stay in the minors, and get called up if deemed worthy.