Can we move him to the bullpen now? If he performs well in short or middle relief, it's the ONLY possible way another team might be interested in him at the trading deadline. Otherwise it's going to be an UGLY scene if he sticks around as his contract expiration approaches.
I will go out on a limb and say he gets 2 more starts before we reach a decision point. There is no minor leaguer who has shown he's ready to take his slot in the rotation and Cavalli and Gray are several weeks away from being considered. Even if you view him as a "7th or 8th" starter, we kind of need him now.
Note that the little flip they did in the rotation of him and Parker not only lined up Parker against the tougher hitting team, but also will make it feasible to skip Corbin when we get out of the 17 games in 17 days stretch we are in. The way the rotation lined up, the next off day would be Corbin's 5th day when he would be due to start (June 10). They can skip him and just keep Parker on his 5th day (june 11) if they want. It probably would be too soon to start Gray or Cavalli on Saturday June 15, but you could maybe see a Herz / Ward / Rutledge that day if they are going well.