Ifill picked up the injury on the opening day of the season, when he was carried off at Home Park against Plymouth, and has struggled to regain his fitness. He broke down again after the games against Wolverhampton Wanderers a fortnight ago and now needs surgery.
"Iffs is due to have the operation on Friday and will be in plaster for a fortnight," explained Lions' Physio Gerry Docherty. "Then he faces another two weeks in an air cast boot, with the rehab process taking eight to ten weeks in all.
"He really has had a wretched season injurywise, but hopefully he'll be back in time to play in the last few games."