Ireland defence coach Les Kiss looks on© Patrick Bolger/Getty Images

Ireland boss Joe Schmidt will struggle to replace "one of the best defence coaches in the world" in Les Kiss, according to Rory Best.

While the Australian has taken over as rugby director at Ulster, Ireland hooker Best has backed head coach Schmidt to pull off another coup.

"I think it will be tough: if you're trying to replace like-for-like in terms of Les, for me he's one of the best defence coaches in the world," said Best. "I'd have no problem standing over that.

"It's going to be very tough, but with Joe there, he managed to make it work when John Plumtree left. Joe brought in Simon Easterby and he's brought different strengths, and I don't think the forward play has suffered any for that.

"Joe knows what he wants, knows what he likes and knows how he wants Ireland to go forward. And he'll bring in someone accordingly."

Ireland must plough quickly through a state of flux after their World Cup quarter-final exit, seeking a new captain after Paul O'Connell's Test retirement.

Peter O'Mahony will be among the front-runners for the long-term job, but Munster boss Anthony Foley confirmed the combative flanker looks unlikely to feature in the Six Nations. O'Mahony is pencilled in for a March return after knee surgery, but that timescale could yet prove optimistic. 

South Africa-born back-rower CJ Stander has now qualified for Ireland on residency, and could yet be drafted into the Six Nations squad. Foley has chosen Stander to captain Munster's Champions Cup matches, and backed the 25-year-old to sustain his fine form with the province.

"Paul O'Connell's gone, and someone else will take up the mantle and we'll get on with it," said Foley. "Talking to him last year before the Toulon thing came up he wasn't coming back to play for Munster so we knew that was happening anyway.

"So it was never in his or my mind for him to be involved this year, so he moves on as others have in the past, and best of luck to him. It's not about replacing Paul O'Connell, it's about the next guys coming in and doing the very best that they can do.

"CJ's been announced as captain for the European Cup group, and that's where we see his influence at the moment. We've got great influence throughout the group, we've got a lot of leaders.

"We can't rely on one person, it's never been the case at Munster, it's always been a group approach, that's always been our strength. The group must be the most important thing.

"He's moved over lock-stock, his girlfriend's over here, he's settled his life in Limerick and enjoying it at the moment. He's really enjoying it, buying in and he's got a great mentality and attitude around the place.

"It should be March in terms of Peter [O'Mahony], it's a fairly lengthy recovery. Big injuries are part of the game at the moment unfortunately. He will come back, it's a long road but hopefully we'll see him before the end of the season."