Cardiff Blues could be without the services of Martyn Williams "for a fair while" because of a second injury to his right arm.
The former Wales international has missed the last three months with a broken bone.
However, he recently returned to training and was expected to make his return during this Friday's Heineken Cup tie with Edinburgh.
Williams now faces the prospect of having a metal plate inserted in his arm following a setback in training.
"Martyn has had a recurrence of the injury, which is very disappointing," said Blues coach Justin Burnell.
"He's been set back for another period. He had a knock on his arm during a very physical session which was required for the squad, so he's gone back now to have more X-rays.
"We could be without him for a fair while. He's gutted. I felt very sorry for him because we had included him in the squad for this weekend."
Williams, 36, has made 99 appearances for the Welsh national team.
