ARLINGTON, Texas (AP) — All-Star knuckleballer Tim Wakefield is headed to the disabled list because of a lower back problem.

The Boston Red Sox recalled right-hander Clay Buchholz from Triple-A Pawtucket to start in Wakefield’s place Wednesday night in the finale of a three-game series in Texas.

Manager Terry Francona said Wakefield, who turns 43 next week, got hurt throwing on the side Saturday.

Wakefield said he wasn’t exactly sure when he got hurt or when he will try to throw again, though he didn’t sound overly concerned.

“It’s a minor setback, that’s all,” Wakefield said.

The DL move is retroactive to July 18, meaning Wakefield will be eligible for reinstatement Aug. 2, which is his birthday.

Wakefield, who described having a “sharp pain in my glute area,” said he first felt a twinge on the way to Toronto for the first series after the All-Star break.

“I had a lot of work to do, threw a simulated game, I felt fine. Then afterward it tightened up on me,” he said. “I’m trying to make it get better, getting treatment every day, but it doesn’t seem to be going away right now.”

Wakefield (11-3) last pitched July 8 against Oakland, when he allowed three runs over six innings for a victory, and is 5-0 his last seven starts. He didn’t pitch in his first All-Star game and has a 4.31 ERA this season.

“Something’s not right in there. My hips might not be aligned right having not thrown on the mound for a week and then getting back on the mound, it might have jarred something in there that caused a big spasm,” Wakefield said.

Buchholz started Boston’s first game after the All-Star break, earning a victory Friday against Toronto in his only major league start this season before being sent back to the minors. That spot start was designed to give Wakefield and the rest of the Red Sox starters extra rest.

“An extra week isn’t going to hurt anything and might be better,” Wakefield said.

“We’re going to try to make it be good. We didn’t want him to be hurt like this,” Francona said. “Rather than push a start, it didn’t make much sense. So we’ll try to use this to our advantage, try to get him to come back where he left off.”

Buchholz threw five scoreless innings for a victory in his only career appearance against Texas on April 21, 2008.

He got a call at 1:30 a.m. Tuesday that he was rejoining the Red Sox to start on the fifth day for them rather than for Pawtucket.

“With all the expectations, I was pretty nervous. But I got that win under my belt, now I’m just trying to throw strike one,” the 24-year-old Buchholz said. “This is an odd situation, but I feel really comfortable. Things have a way of working themselves out.”