Martyn Williams has endured a setback in his recovery from a broken arm as the veteran Cardiff Blues flanker suffered 'a knock' in training.
The 36-year-old was hoping to make his comeback in Blues' Heineken Cup clash against Edinburgh on Friday but he now could be out until the new year.
But coach Justin Burnell said: "He's had a bit of a setback unfortunately."
Williams suffered the fresh injury on Tuesday and the Blues openside will undergo further scans before the Welsh region confirm a new comeback date for the 99-times capped Welshman.
"He was in the squad for Friday's game with Edinburgh but he had a bit of a knock," said Blues boss Burnell.
"He was the first to come in on Monday morning to tell me he was available and could be announced in the initial squad.
"He was taken from the field with our physios and we're just waiting on the results for the X-rays on his arm.
"So that was a bit of a setback because he has been fantastic for the period when he was injured. We're hoping it is not too serious."
Josh Navidi played at openside for Blues in their 52-9 defeat in Leinster on Friday but Wales captain Sam Warburton is expected to return from international duty to play at number seven against Edinburgh in the Heineken Cup on Friday.
Williams' initial injury dashed his World Cup hopes as the experienced forward hoped to win his 100th Test cap.
"It appears to me, unfortunately for Martyn it's going to be 99 and out," said former Wales number eight Emyr Lewis.