"He's got a history of issues," said Red Sox manager Terry Francona. "That's why I think we're being somewhat cautious. We would like to have him for the whole year, and not just have him, but be productive and healthy. When something like this happens, we're going to stop it, because we kind of like the way he's been throwing."
Justin Masterson, who has turned in one quality outing after another, can now remain in the rotation for a couple of weeks, even with Daisuke Matsuzaka returning on Saturday.
"Fortunately we do have some safety in numbers, but it's not just numbers but quality guys in the rotation so we can be cautious to let the aches he's feeling quiet down," said Red Sox pitching coach John Farrell.
Putting Colon on the DL seemed like a pretty obvious decision for the Red Sox.
Right-handed reliever Chris Smith was recalled from Triple-A Pawtucket to take Colon's place on the roster. Smith will go back to the Minors on Saturday when Matsuzaka is activated.
Colon's next turn in the rotation was to be on Tuesday, when the Red Sox play host to the Diamondbacks at Fenway Park. But the combination of the off-day on Thursday and Matsuzaka's return gave the Red Sox some flexibility.
Masterson, who is pitching against the Phillies on Wednesday, will take the ball in Colon's original spot on Tuesday.
Colon, a free agent signing during the offseason, is 4-2 with a 4.09 ERA in six starts. Smith, 27, had eight saves, a 1.52 ERA and 40 strikeouts in 41 1/3 innings for Pawtucket. He has never pitched in the Major Leagues, though he did spend one day on the roster earlier this season.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.