Munster coach Johann van Graan said he awaited confirmation on the exact nature of Tommy O'Donnell's injury but he said he suspected that the back row forward had suffered a broken leg.
O'Donnell was carted off just before half-time in Munster's 36-22 win over Gloucester in the Heineken Champions Cup clash in Thomond Park.
The flanker was not the only Munster player to incur an injury in the win with Dan Goggin and Rhys Marshall suffering knee and upper leg injuries respectively.
Like O'Donnell, Goggin has had rotten luck with injury, having been sidelined for five months with a knee injury at the end of last year.
Speaking afterwards, Van Graan said his side paid a heavy price injury terms in the victory over Gloucester.
"Tommy’s gone to hospital. No confirmation yet but I believe he broke his leg and Dan Goggin looks like a serious knee injury. We also lost Rhys Marshall which looks like a serious upper leg injury. We will know more on Monday."