O’Brien struggled with the same problem last year and as a result will miss Ireland’s Autumn Internationals where they take on Argentina, South Africa and Fiji.

He told the Irish Independent: "Sean's most recent operation was last week. He's feeling pretty good about the operation.

"It will be a long, slow process. There weren't any complications. It was two different operations. We're hoping he'll be back mid-December."

Other long-term concerns for the reigning Heineken Cup champions are Ireland internationals Eoin O’Malley and Rhys Ruddock while Luke Fitzgerald won’t be back in action until 2013.

"A couple may be back next week,"added Schmidt. "The vast majority will come back in weeks three and four. One of the difficulties for us is suddenly implanting ten changes in your starting line-up.

"The problem is you would have no continuity with them. So they're starting back on the field with us and we'll integrate them as best we can."