Blair has won 37 caps for Scotland

Blair faces around six to eight weeks out of action after suspected ligament damage sustained playing for Edinburgh last Friday was confirmed on Tuesday.

Even the best-case scenario will mean him missing the matches against England (3 February) and Wales (10 February).

Scotland are already set to be without Chris Cusiter for much of the campaign.

The Borders scrum-half injured his shoulder against the Pacific Islanders in November and was initially ruled out of action for four months.

He remains hopeful of being available for Scotland's final three matches, starting against Italy on 24 February, after a visit to his surgeon on Tuesday.

I wouldn't worry about putting Rory in against England Former Scotland scrum-half Bryan Redpath

But the absence of both players leaves coach Frank Hadden short of experienced cover.

Gloucester's Rory Lawson, son of former Scotland scrum-half Alan and the grandson of legendary commentator Bill McLaren, could make his first Scotland start against England at Twickenham.

The 25-year-old made his debut off the bench in the autumn, as did Sam Pinder, the other contender for the number nine spot, although he is currently being kept out of the Glasgow team by veteran Graeme Beveridge.

Scotland's most-capped scrum-half Bryan Redpath, now Lawson's backs coach at Gloucester, believes he is ready for the step up.

"I have no doubts Rory deserves a chance," Redpath told The Scotsman. "I wouldn't worry about putting him in against England.

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"I told him when he came to Gloucester that he would be behind Peter Richards initially and it was up to him to dislodge him, and he's done that.

"What has put Rory ahead is probably the fact that he sticks to the script.

"He is not a flashy player, but he has a very high work-rate, he does the basics very well and has a very accurate kicking game."

The centre is ahead of schedule in his recovery from the knee injury he sustained during his try-scoring Test debut against Romania in November, but should return to full training next week.

Scotland wing Chris Paterson sustained soft tissue damage to his back against the Scarlets last Friday, but should be available for selection for Edinburgh's Heineken Cup clash with Leinster on Saturday.

The 30-year-old's contract was due to expire next year.

The former Waikato Chiefs and Llanelli Scarlets forward moved to the Scottish capital a year ago, but he has been out of action in recent weeks with a rib injury.

Meanwhile, a scan has revealed that Duley's fellow Kiwi Matt Mustchin has suffered severe bone bruising and soft tissue disruption, rather than a fracture, to his shoulder.