Ireland flanker Sean O'Brien could return to action before this season's Six Nations after being ruled out for eight to 12 weeks by his broken arm.
The British and Irish Lion, who plays for Leinster, sustained the injury in Ireland's win over Argentina on 10 November.
O'Brien has had "a surgical procedure for a forearm injury", Leinster said.
Last season's Grand Slam winners open their Six Nations campaign against England in Dublin on 2 February.
Leinster added that Ireland centre Robbie Henshaw will be out for four to six weeks because of the hamstring injury suffered in the warm-up before the Argentina game.
An eight-week timeframe would see O'Brien back in action in early January.
But if he needs a further month of recovery, he could miss the start of Ireland's Six Nations defence.
The Irish travel to to Murrayfield to face Scotland in their second match on 9 February.
Flanker Dan Leavy will not be considered for Leinster's Pro14 game against Ospreys on Friday because of the neck strain which forced his late withdrawal from Ireland's game against New Zealand.
Utility back Joe Tomane will be missing from Leinster duty for up to five months because of a serious hamstring injury while Fergus McFadden (hamstring), Rory O'Loughlin (knee), Will Connors (ACL) and Barry Daly (knee) are also out of action.