Cardiff Blues have confirmed Blair has a very small fracture in a bone in his right hand, which has been put in a cast to protect it.
Blair will see a hand specialist on Monday and it is thought that the injury could keep him out of action for up to four weeks.
The New Zealand international fractured the 4th metacarpal bone in the match against the Ospreys on New Year’s Eve and his hand is now healing in a splint.
This means the the goal kicking Kiwi will miss the crucial match with Gloucester at the end of the month.
The Blues may have a 100 per cent record in Pool 6, but with Gloucester also performing well, the Kingsholm tussle is likely to be a Pool decider, and the Blues know only too well the cost of coming second in the group stage.
Failure to progress in first place last season meant a trip to Toulouse in the quarter-finals of Europe toughest club competition. The result went the way of the three-times champions and now, Blues boss Dai Young must wait on medical results to see if his goal-kicking full back can help his side into the final eight.
Blair walked off midway through the first half with an ice bag on his hand during his side’s 16-12 defeat to their regional neighbours.
Meanwhile, Martyn Williams, the Wales and Lions flanker, was another to leave the field clutching his shoulder, but he is expected to be fit.
“Martyn has struggled throughout the Autumn Test series with a shoulder injury,” said Young.
“We rested him for two weeks and he just took another bang on it. There is nothing which needs an operation and nothing to be worried about there.”
