Manager John Farrell said Wednesday that Masterson was would not start this Sunday due to arm fatigue, which he pointed to as possible explanation for Masterson's diminished arm strength over his last two starts. In losses to the Tampa Bay Rays and Oakland Athletics, Masterson allowed 10 runs on 13 hits over 6 2/3 innings, walking seven batters while striking out three. Masterson lasted 4 1/3 innings against the Rays on May 6 and only 2 1/3 against the A's Tuesday.
"I'm not real happy about it. I'm mad," Masterson said, according to MLB.com. "Like I said [Tuesday], I hold true—just the fact that I felt like we could make the adjustment and get back out there and really be fine. It didn't happen. It comes a time with this team when we're starting to pick it up, but it's one of those where if we're doing great, I probably get a little more leeway."
The Red Sox won Masterson's first three starts to begin the season, though he was credited with wins in only two. Since then, they have lost his last four starts and Masterson stands 2–2 with a 6.37 ERA over 35 1/3 innings.
The Red Sox entered Wednesday 15–18, 5.5 games behind the New York Yankees in the AL East.
Farrell said knuckleballer Steven Wright could replace Masterson in Sunday's start at the Seattle Mariners, but he will not decide until Thursday. Lefthanded reliever Robbie Ross was called up to take Masterson's spot on the roster.
- Mike Fiammetta