Time to call up EdRo and see what he has. The next 10 games are somewhat important (TOR 3, BALT 4, TOR 3) and Clay's clear lack of confidence would be feasted upon by those hitters.
Option 1: 'Mental DL stint' - Get Clay get out of Boston, take a few weeks off and get a breather. Take MRIs, look at his diet, his work out regime, get him into yoga/meditation, some Zen shit- whatever clears out the squirrels. Look at some video with Bannister and Willis (have some vets, that Clay may respect, add a voice like Pedroia/Papi/Price), then head to Florida for 2 weeks to work on his stuff with a personal coach. Start over at Pawtucket by the end of June, like its Spring Training, and see if he can be productive for a post All Star run. Elias can be the #6 man in Pawtucket in case of injury for the next 6 weeks. If Clay shows life at Pawtucket, work him back into the rotation for whomever is ineffective or needs a mid-season breather.
Of course we'd need Clay to be a team player and agree to something like that.
Option 2: If he refuses the 'Mental DL stint', then send him to the pen, he can be the long man/mop up pitcher. I'd give him till All Star break to figure it out in the pen and if he can't we'll have Workman, Light, Martin, Elias, Ramirez, etc to come up at that point.
I wouldn't deal him for pennies on the dollar or DFA him at this stage. Its a long season and we've seen guys make comebacks before.