Rob Gronkowski is heading back to the operating room.

The Patriots tight end will undergo back surgery in mid-June, according to a source.

The source said the procedure will keep Gronkowski out for at least the start of training camp, but the Herald reported last week that the expectation would be for him to be sidelined until late-September in the event of back surgery, which will remove part of a disc that caused discomfort last season. It’s unclear if the timetable for recovery has changed, or if the earlier return date is simply more optimistic.

Dr. Robert Watkins, who performed the surgery on Gronkowski’s back in 2009 when he was at the University of Arizona, will operate again. Gronkowski missed the 2009 season with the Wildcats, which caused him to fall into the second round of the 2010 draft.

The Pats have been bracing for this news. Gronkowski played through a great deal of back pain last season, and all sides knew surgery was a possibility this offseason. Before anything, though, they had to rid his surgically repaired left arm of a troublesome infection.

The major question now is when Gronkowski can return. If he makes it back during training camp, there will be some optimism about his availability for the start of the regular season. Yet, if the late-September timetable holds true, the Pats could opt to place Gronkowski on the physically unable to perform list, and he would miss at least the first six games.