The Ospreys have suffered a blow ahead of next week's Heineken Cup opener against Leinster after flank Ryan Jones suffered a calf strain.
Jones was expected to return to action this Friday against Ulster in the PRO12 after a long period out of the game recovering from a shoulder injury.
But it seems the 32-year-old is definitely ruled out of that game at the Liberty Stadium and is a doubt for the Heineken Cup match at the same venue.
"The problem Ryan has got is he trained last week and he pulled up with a calf strain," Ospreys' forwards coach Chris Gibbes told Wales Online.
"It's bad enough for him not to be able to play. We are feeling for him.
"He's a huge part of our squad. To have a guy like that involved in your squad is massive. It's unfortunate for Ryan but others get an opportunity."