Justin Masterson failed to get through the third inning on Tuesday night as the Boston Red Sox lost 9-2 to the Oakland Athletics.
In his previous start, Masterson walked six batters in less than five innings.
John Farrell suggested after the game that there might be issues that would require him to pull Masterson, 30, from the rotation.
"The last two times out for Justin have not been anywhere close to what he's shown this year -- set aside prior to the start of 2015," Farrell said. "Clearly, he's not right. Whether that's physical, whether that's delivery-wise, the ball is not coming out of his hand as he's shown the better part of the year. We've got to gather information, we've got to check on him in the morning, get a full workup, get a better assessment of where things are."
Masterson has a 6.37 ERA, 1.67 WHIP and 24 strikeouts against 19 walks in seven starts (35.1 innings).
"Talking to the medical staff right now and to Justin himself, it's not anything glaring -- an area of the body that can be identified to say this is the primary reason," Farrell said. "To what extent he feels something that might subconsciously be in there and not allow him the freeness and the ability to cut the ball loose, that's what we're trying to work to the bottom of."