BOSTON – Already out 2 1/2 weeks with a neck injury, Red Sox pitcher Clay Buchholz cut short a bullpen session Wednesday and was scheduled for a medical scan.

Buchholz (9-0) has been on the disabled list since June 9 with a neck strain. With the team’s cable network showing Manager John Farrell and pitching coach Juan Nieves watching, Buchholz stopped throwing after about 18 pitches. He talked with the pair before walking to the clubhouse.

“The positive in this is that he threw today as intense as he did yesterday from flat ground,” Farrell said. “The ball was getting out of his hand good. When he got on the mound and got into his bullpen, he still feels some restriction in that same area, so he’s scheduled for an MRI later today and we’ll have more information following that.”

Boston had hoped Buchholz would be able to pitch Tuesday night, but Ryan Dempster made that start against Colorado.

“He’s not at the point of being able to do a normal bullpen in advance of any rehab start,” Farrell said.

The 28-year-old right-hander leads the majors with a 1.71 ERA. He made an early exit from his last start against the Los Angeles Angels on June 8 after feeling discomfort in his neck following an off-balance throw to first. Also in that game, he did a summersault after making an awkward tag at first.

He also missed a turn earlier this season because of irritation in his right collarbone area.

BOSTON ACTIVATED right-hander Clayton Mortensen from the 15-day DL after optioning righty Pedro Beato to Triple-A.

Mortensen had been placed on the DL on June 11 with a strained right groin. He was 1-2 with a 5.34 ERA before the injury.

Beato was recalled from Pawtucket on Tuesday when left-hander Franklin Morales was placed on the 15-day DL with a strained muscle on the left side of his chest.