Alfredo Aceves will take Lackey's spot in the rotation and pitch Thursday night against the Orioles. Felix Doubront, who was originally slated to take that turn, will instead go Friday night against the Rays.
"We wanted another right-hander in this ballpark against Baltimore," said manager John Farrell. "Alfredo has had some good performance numbers against some individuals in their lineup, particularly [Matt] Wieters. Keeping him from the left side of the plate was probably -- well, it was one of the factors in that."
A couple of days ago, the Red Sox thought there was at least a chance Lackey could just miss one start and avoid a trip to the DL.
"He went through some light throwing and the biceps still had some stiffness to it," said Farrell. "Not knowing how many days he'll have to have that irritation completely resolved, we just felt like it was in his best interest to put him on the DL, let that recover at its own rate and not he feel like he's up against the calendar and forcing things to get back to the mound. Again, his health and well being is first and foremost in this."
After undergoing Tommy John surgery that led to a 17-month recovery, the last thing Lackey wanted was another injury, but he's glad this one appears to be nothing more than a bump in the road.
"I'm not going to throw for a couple days," Lackey said. "I'll just get treatment, that sort of stuff and hopefully get that tight feeling out of there before I start throwing. I mean, I knew it was a little tight. I thought it might loosen up when I threw, but it didn't really loosen up."
Right-hander Alex Wilson, who has never pitched in the Majors, was summoned from Triple-A Pawtucket to take Lackey's spot on the roster. He will pitch out of the bullpen.
Wilson made two appearances for Pawtucket this season, posting a 10.12 ERA over 2 2/3 innings.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.