Munster back Keith Earls faces a spell on the sidelines
Keith Earls will be out of action for four to six weeks after a scan confirmed he has sustained medial ligament damage.
The Ireland and Munster wing picked up the injury in the opening seconds of his province's Pro12 clash with Leinster on Friday night.
If Earls' injury enforced absence is at the shorter end of the expected scale, he could yet be in position to feature in Munster's back-to-back Heineken Cup pool games against Llanelli Scarlets in mid-December.
The two-time European champions get their campaign underway against Northampton on Saturday evening, and travel to play Castres Olympique away a week later.