McFadden’s Leinster team-mate Luke Fitzgerald is also facing a race against time to return from long-term groin trouble for Ireland’s November Tests, against South Africa, Georgia and Australia.

Leinster coach O’Connor believes McFadden’s injury is not as bad as first feared, but the 28-year-old still swells Ireland’s list of likely autumn absentees.

Sean O’Brien was ruled out for six months with shoulder trouble last week, while Cian Healy is sidelined for five months with hamstring problems.

Ireland boss Joe Schmidt will also be forced to go without long-term Ulster absentees Iain Henderson and Dan Tuohy, while fly-half Johnny Sexton is expected to be fit despite still recuperating from a broken jaw.

“Ferg obviously was a pretty high-profile departure, he’s reported significantly better than we had hoped post-game,” said O’Connor.

“And it looks like a pretty significant ankle strain which will tie him down for about six weeks, but no surgery or other intervention which is really positive.

“He didn’t look in a great place and you always fear the worst when guys are stretchered off the field with a lower leg injury.

“He’s recovered quite well and the scan results were positive, so it’s crack on now with the rehab and try and get him back out on the park as quickly as possible.”

Fitzgerald has not played since suffering groin trouble in March and O’Connor admitted the 27-year-old will still require a fortnight of reintegration once back to full fitness before he can return to action.

“How long is a piece of string?!” added O’Connor.

“Jokes aside Luke’s progressing really well, he’s putting in some positive strides; he’s not very far away.

“What we’ve outlined with him and the medical staff is that once he’s running flat out and changing direction we’ll bring him back into the rugby programme and see how he progresses.

“When that happens there’s probably a two-week window where he needs to do the rugby training, he’s missed a hell of a lot of the rugby programme since Christmas.

“So we need to give him the best chance to get his groin right then get reacquainted with a rugby ball and his team-mates.”

O’Connor admitted Leinster must “find a different way to win” without talismanic ball-carrying duo Healy and O’Brien, intimating Ireland will be forced to follow suit in the autumn.

Player welfare has rocketed back to the top of world rugby’s agenda with a spate of early-season injuries, Leicester Tigers most dogged among Europe’s elite.

Former Leicester coach O’Connor said it is too soon to gauge whether injury rates are increasing, aiming to lean on long-term planning to offset his own lengthening list of absentees.

“You have to work out a different way to win and that’s a job for the coaches to work out our competitive advantage against the opposition,” said O’Connor.

“It’s hard to say whether injuries are increasing: you legislate for 20 per cent of your squad injured at any one time.

“That’s the number bandied around by professional organisations all the time.

“There are a whole load of contingencies that go in and around that with planning.

“From that end it’s a part of the actual process in strategic planning.

“It’s frustrating but there’s nothing you can do when guys are getting broken in games, unfortunately that’s the level of commitment required in the modern game.

“It’s something you try to manage, I don’t know if it’s more or less, but the commitment from the lads is unbelievable.”