GREEN BAY, Wis. -- Packers center Corey Linsley is recovering from ankle surgery that could keep him out for part of the offseason program, sources told ESPN.

One source described the procedure as a "clean-out to remove loose particles" stemming from the high ankle sprain he sustained late in the 2015 season. That injury, according to the source, is believed to have contributed to the hamstring injury he sustained last offseason that kept him out until Week 9 of last season.

"The doctors believe he was compensating for the ankle, which put a strain on his hamstring," one source said.

Linsley and JC Tretter have spent the past three seasons handing the starting center job back and forth. Tretter was slated to start in 2014 until a knee injury late in the preseason forced Linsley into action as a rookie. He played every snap that season and the first nine games of 2015 until he sprained his right ankle against the Minnesota Vikings.

Tretter started three games late in the 2015 season while Linsley dealt with the ankle injury before he returned for the playoffs. Tretter took the job back again last season after Linsley's hamstring injury in an offseason workout forced him to start the season on the physically unable to perform list. Linsley was activated off the PUP list just as Tretter sustained a knee injury in Week 8.

Tretter will be a free agent Thursday if the Packers don't re-sign him.

Linsley is expected to be cleared for offseason workouts by mid-May, one source said, but there is a chance the Packers will hold him out until training camp just to be safe. That could leave Jacob Flores, an undrafted rookie who spent all of last season on the practice squad, as the only center available when the offseason program begins next month.

Linsley's surgery was performed by Dr. Robert Anderson in Charlotte, North Carolina, shortly after the Packers lost in the NFC Championship Game, a source said. Anderson has operated on several Packers players recently, including Eddie Lacy and Ty Montgomery, and is in discussions to move his practice to Green Bay and partner with Packers physician Dr. Pat McKenzie when a new sports medicine clinic opens later this year in the Titletown District development that is under construction adjacent to Lambeau Field.