BOSTON (AP) – Bartolo Colon had a setback in his attempt to return to the big leagues with the Boston Red Sox.

The 2005 Cy Young Award winner, who is pitching for Triple-A Pawtucket, strained his right side. He was placed on the seven-day disabled list Monday and will miss at least one start.

Colon will be re-examined Tuesday in Boston before the home opener against Detroit, manager Terry Francona said.

“I don’t think there’s anybody (who) thinks this is anything” major, Francona said. “There was not a lot of complaining on his side of this. It was more the trainers and the medical people in Pawtucket (who) said, “OK, he has this. Let’s stop it.”‘

The right-hander will be eligible to come off the disabled list on Friday.

In his only appearance for Pawtucket, Colon, who signed as a free agent during spring training, pitched five scoreless innings Thursday and earned the win in a 3-0 victory over Indianapolis. He struck out five and allowed one hit and one walk on 74 pitches, 45 of them strikes.

Chris Smith was promoted from Double-A Portland to start in place of Colon.

In other news, Boston right-hander Mike Timlin, on the disabled list after cutting his right ring finger when it was struck by a ball hit to him, pitched one scoreless inning Monday night in a rehab assignment for Pawtucket. He struck out one and allowed two hits against Lehigh Valley.