Clay Buchholz leaves with right-elbow tightness, taken for MRI

BOSTON -- Clay Buchholz, Boston's best pitcher for the past two months, left in the fourth inning of Friday night's 5-1 loss to the New York Yankees with what the club later called right-elbow tightness.

Buchholz, trailing 1-0 after giving up a home run to Alex Rodriguez in the first inning, was pitching to Yankees second baseman Stephen Drew with one out and runners on second and third when catcher Sandy Leon went to the mound after his 0-and-1 pitch and put his arm around Buchholz's shoulder.

"At first, he was throwing the ball really well,'' Leon said. "The last pitch he threw was a cutter, which is normally 88, 89 [mph]. The last one was 85. He called me and said there was something with his elbow. I said to him, 'You've got to be smart. We've got three months to go. I'll call John [Farrell].'"

Leon signaled to the dugout, bringing manager John Farrell out at a trot, with trainer Rick Jameyson close behind. After a brief consultation, Buchholz left the mound with Jameyson.

"[He] didn't feel like he could push through it at that point,'' Farrell said.

Buchholz was taken to Massachusetts General Hospital for an MRI and other imaging. Farrell offered no further update on his condition.

"There's some tightness, some stiffness in the elbow area,'' Farrell said. "He's undergoing the full workup with imaging. Until we get any further information, that's all we have right now."

Buchholz entered Friday's game the winner of five straight decisions. Over his previous 10 starts, he was 5-2 with a 1.99 ERA, a huge contrast to his first seven starts (2-4, 5.73). Before Friday's game, Farrell had praised Buchholz for his ability to throw four pitches for strikes and said Buchholz was repeating his delivery better than he had in his eight seasons with the club.

But he has had trouble staying healthy.

Buchholz, who turns 31 on Aug. 14, has been on the disabled list in each of the past five seasons, with shoulder bursitis in 2013 sabotaging the best start of his career, when he went 12-1 with a 1.74 ERA and was named to the All-Star team. Last season, he was sidelined with what the club called a hyperextended left knee; in 2012, he was rushed to the hospital with internal bleeding caused by esophagitis; in 2011, he had a stress fracture in his lower back; and in 2010, he strained a hamstring running the bases in San Francisco.

For those reasons, Buchholz never has reached 200 innings or 30 starts in a season.