The 30-year-old forward had an operation after pulling out of the England squad for last week's International Origin match against the Exiles through injury. O'Loughlin had missed the Warriors' Super League defeat of Widnes the previous week with the problem.
Warriors coach Shaun Wane said: "It's not gone too bad, so he'll be there or thereabouts in about five weeks from now. It was a six to eight-week operation. You have to look at this as a positive."
He added: "Rugby players have operations, they get knocks, but the plus side for Sean is he'll have two months where his body is going to repair. He'll come back a different player for a really important end of the season, when we'll need him most."
Wigan have a lengthy injury list with Michael McIlorum, Ben Flower, Gil Dudson and Blake Green sidelined, while there are doubts over Matty Smith, Darrell Goulding and Iain Thornley ahead of Monday's trip to Warrington.
Wane had hoped stand-off Green, out since suffering an ankle strain in the Challenge Cup win over Hull KR six weeks ago, would be fit by now but he remains among the casualties.
Wane said: "It is one of those sort of injuries where you can't really put a definitive time-frame on it. He can be three, six, eight weeks. But he is a good pro and has worked hard on his rehab. He'll be back as soon as he can but I think this game is probably a couple of weeks too early."
Wigan are set to welcome back Sam Tomkins, Pat Richards and Liam Farrell from the side which beat Widnes 33-32 a fortnight ago.
Meanwhile, former Wales rugby union international Andy Powell, whose signing from Sale Sharks was announced in April, is now training with the Warriors after a shoulder injury.
When fit and deemed ready, Powell is likely to be given the chance to find his feet in rugby league with games for Championship club South Wales Scorpions, with whom Wigan have a partnership.
- Sports & Recreation