The slumping Boston Red Sox will have a new pitching coach for the remainder of their tumultuous first season under manager Bobby Valentine.

Bob McClure was fired Monday and replaced by Randy Niemann with the Red Sox on the fringe of the playoff race following another rough stretch.

“We felt like we needed to make a change to put our pitchers in the best position to do what they needed to do,” general manager Ben Cherington said. “The next six weeks are important to create a foundation going into the offseason. We felt like this change was needed to give ourselves the best chance to do that.”

The Red Sox have lost 12 of 18 games this month to fall off the pace in the competitive AL East. Boston’s 4.30 team ERA was 11th in the American League heading into Monday’s games.

“This is a performance-based decision,” Cherington said. “As I said yesterday, there’s been a real good effort on the part of the staff to work together and iron out any communication issues that may have existed previously. This decision had nothing to do with that.”

Boston has struggled in its first year under Valentine, who took over in December after agreeing to a two-year deal with club options for 2014 and 2015.

Popular infielder Kevin Youkilis had a public dustup with Valentine before he was traded to the White Sox, and Yahoo Sports reported that several players met with owner John Henry and team president Larry Lucchino in New York last month to complain about the manager’s handling of the team.

The Red Sox (59-63) were off Monday and host the Los Angeles Angels in the opener of a three-game series on Tuesday night.

The 60-year-old McClure became the pitching coach in December. He also spent six seasons in the same position with the Kansas City Royals. The left-hander was 68-57 with 52 saves and a 3.81 ERA in 19 seasons in the majors.

Niemann was elevated from assistant pitching coach. He is in his first year with Boston after spending 24 seasons in the New York Mets’ organization.

“Randy’s got a lot of experience, too,” Cherington said. “He knows our guys well.”

The Red Sox also will be without outfielder Carl Crawford for the remainder of the season. He is scheduled to undergo season-ending surgery on his left elbow Thursday.