Conor Murray is in danger of missing Ireland's November internationals as a result of the neck injury that will keep him out of the start of Munster's season.
The province have recruited All Black Alby Mathewson on a four-month deal after losing their most important player for their opening Guinness PRO14 games and the first two rounds of the European campaign.
Munster's statement described Murray's injury as "short-term", while the IRFU were unable to provide further detail but the Irish Independent understands that he could be out until December, putting him in danger of missing Ireland's clashes with Argentina and New Zealand.
It is unclear at this point if the problem will require surgery.
Elsewhere, former Leinster fly-half Jimmy Gopperth is out for the season after suffering a cruciate injury, meaning the Wasps man won't face his old club in their Heineken Cup pool games.