"Keith Earls will have a scan on Monday to determine the exact extent of the damage he sustained to his knee on Friday night. While it's not known at this stage how long he'll be sidelined, he will not be available for Munster's November Heineken Cup games," explained a Munster press statement.
Munster open their 17th Heineken Cup campaign with a home clash with last season's runners-up, Northampton Saints at what is set to be a 26,000 sell-out Thomond Park. The Irish province twice beat Saints in Limerick in the 2009/10 season, 12-9 win the Pool stages and 33-19 in the quarter-finals.
Earls will also miss the trip to France in Round 2 when Munster face Castres Olympique at Stade Ernest Wallon. The Scarlets are the other team in Pool 1.