PAWTUCKET -- Felix Doubront left his start Tuesday night after his right hamstring cramped up on him, PawSox manager Arnie Beyeler said.

"He came in here and did some squats after he came out of the game," Beyeler said. "Who knows? Muggy night. We were going to err on the cautious side with him."

The 23-year-old righty had pitched into the fifth inning when his right leg appeared to buckle on the 69th pitch he'd thrown in the game. He reached back toward his hamstring immediately with his glove hand, and he didn't even try throwing any pitches off the mound before trudging to the dugout.

He left the clubhouse just before reporters were allowed inside, but he did not appear to be limping on his way out.

"We have to re-evaluate him tomorrow and see how he comes in and go from there," Beyeler said.

Doubront missed several weeks in spring training with an elbow injury, and a groin injury cost him most of the month of May.

Doubront had felt some discomfort in his hamstring in his start for Double-A Portland in Manchester, N.H., before the All-Star break, but it looked at the time like a false alarm. Given how hot and humid it was at McCoy Stadium on Tuesday, the early exit might well be another false alarm.

"It seems like he gets a little tired in that (pitch-count) area a little bit, for whatever reason," Beyeler said. "He was throwing good today, throwing easy, and it just grabbed him a little bit. We weren't going to mess with it."

Doubront has a 3.28 ERA in 65 1/3 innings pitched this season, including 4 1/3 innings on Tuesday in which he struck out three, walked two and allowed one earned run on three hits. All three of his strikeouts came on offspeed pitches, and he generated a handful of swings and misses with his changeup.

"He threw a handful of good changeups and, probably, a handful of not-so-good ones," Beyeler said. "He threw maybe a handful of good breaking balls. He was very inconsistent with the offspeed, but he threw probably five of each that were pretty good pitches, very quality ones that helped him out."

Twitter: @brianmacp