Clermont and France international wing Aurelien Rougerie will be out of action for at least three months after sustaining a hernia injury.
The ASM captain, who was joint top try scorer in the Heineken Cup last season with five tries, looks unlikely to feature in any of the French championship finalists' opening four Heineken Cup Pool 1 games.
The 2007 European Challenge Cup winning captain is expected to under go shoulder surgery in the coming weeks and will also be unavailable to France for their November tests against Australia, Pacific Islands and Argentina.
The injury news is another blow for ASM who have suffered two losses in three outings in the new Top 14 season.
ASM's European campaign will get under way without their influential captain when they welcome Sale Sharks on Saturday, 11 October.
As part of the build-up to next month's Cardiff 2014 Heineken Cup and Amlin Challenge Cup finals weekend, ERC has joined forces with the WRU, Cardiff Blues and adidas to develop an annual grassroots community rugby programme targeting young players.
The Ulster Rugby full back, Jared Payne (No 15), has been suspended for two (2) weeks following an independent Disciplinary Hearing in Dublin arising from the Heineken Cup quarter-final match against Saracens at Ravenhill Stadium on Saturday, 5 April.