Date: Sunday, 8 February Kick-off: 1500 GMTVenue: Murrayfield
Coverage: Screened live on BBC ONE Wales and online plus full commentary on BBC Radio Wales, BBC Radio Cymru and online & score updates on BBC Radio Five Live
Mike Phillips and Mike Blair are vying for the Lions scrum-half berth
Mike Phillips and Mike Blair go toe-to-toe in a battle of the probable Lions Test scrum-halves as a sub-plot to Wales' Six Nations opener in Scotland.
Welshman Phillips and Scottish skipper Blair are tipped as favourites to play in the Test team against South Africa.
The pair go head-to-head at Murrayfield and hope to catch coach Ian McGeechan's eye ahead of the summer tour.
"I'm aware it is a chance to show who's best," said Phillips. "And we all know what is at the end of the season."
Welshman Dwayne Peel was the Lions Test scrum-half during their unsuccessful tour of New Zealand in 2005.
Mike is a very good ball-carrier, makes a lot of breaks and has a bit of subtlety about his game
The Sale Sharks star is a late call-up to the Wales squad as cover due to knee injury victim Gareth Cooper.
All three Welsh number nines are in with a shot of making McGeechan's squad for the summer trip to the world champions while Ireland's Tomas O'Leary and England duo Danny Care and Harry Ellis are also in contention.
But Phillips and Blair are the two expected to be battling for the starting spot in the Lions Test team in South Africa.
Blair, a noninee for IRB International Player of the Year in 2008, does not regard Sunday's Six Nations fixture as a straight shoot-out between the two of them.
"I've not given the Lions much thought," said Blair. "All I want to do is a good job for my country, lead and play well, make decisions to benefit the team that will go a long way to further achievements.
"In every game you want to beat your opposite man, that's something that keeps me going.
"Mike is a very good ball-carrier, makes a lot of breaks and he has a bit of subtlety about his game.
"And he has returned to form very quickly after his injury."
Phillips suffered nine months on the sidelines following last year's Welsh Grand Slam victory after a serious knee injury.
"I'll be trying to do my job as well as I can," said the Ospreys star.
"It is vitally important I concentrate on my job with Wales, perform well and then I could be in with a shout."