Though Masterson signed with Boston as a starter, he struggled (2-2, 6.37 ERA) before going on the disabled list on May 14, while lefty Eduardo Rodriguez has pitched lights-out since coming up from Triple-A Pawtucket.
To make room for Masterson on the roster, the Red Sox optioned knuckleballer Steven Wright to Pawtucket, though the righty has performed well as both a starter and in relief.
"You know, Steven didn't pitch his way out of here," said Red Sox manager John Farrell. "He's valuable because of his ability to go long when he's pitching out of the bullpen, and he did a solid job when he was in the rotation of holding down that spot. There's a certain level of dependability that he brings. He's the guy with options right now. He finds himself in the unfortunate situation that he's in today."
Wright will get stretched back out as a starter at Triple-A.
Masterson began his career pitching largely out of the bullpen for the Red Sox, but it's been a long time since he's held that role on a regular basis.
At some point, Masterson might be used in righty specialist situations to induce double plays. But there will first be a reentry period for the righty as a reliever.
"You know, he's healthy and I don't anticipate the need for a high number of pitches to get ready, to get loose," said Farrell. "But I think in fairness to our team and to him, we've got to take the first steps in getting him back into a reliever role."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.