GLASGOW hooker Pat MacArthur admits Sunday's Pool Three Heineken Cup clash with Leinster at Firhill will be a test of nerve.

The 24-year-old has become Sean Lineen's first choice in the pivotal front-row position after nudging ahead of Dougie Hall and taking advantage of Fergus Thompson's long-term injury absence.

Former Ayr star MacArthur has excelled having been picked in every one of Warriors Pool Three fixtures, delivering a silver service to the Glasgow lineout.

But with a record-breaking 6,000-plus crowd expected for Sunday's 12.45pm kick-off against the reigning and two-time European champions, he knows his toughest examination awaits.

He said: "It is fantastic to have started in all of our European games but this one is the biggest of the lot. Given it is only my second full season with Glasgow, it has been a tremendous experience and Sunday can't come quickly enough.

"Hooker is a specialised position. When you are about to throw the ball in at the lineout it is as much about nerve as technique and, hopefully, I have done not too badly so far this season."

Sunday's game with Joe Schmidt's men is the key fixture for Warriors as they bid to make the last eight of European rugby's top tournament for the first time.

MacArthur is confident the pack will play their part in what could be the club's finest hour in continental competition.

He said: "Leinster beat us up at the breakdown in the first tie but by the end of the first half we felt that, as a pack, in the set-piece, we were starting to get on top of them. So it is going to be about staying tight as a unit up front."

Elsewhere, uncapped centre Steven Shingler could be withdrawn from Scotland's Six Nations squad after the International Rugby Board (IRB) said he was only eligible to represent Wales.

The Welsh-born Shingler, who has a Scottish mother, was included in Scotland's Six Nation's squad for their opening two matches, against England and Wales.

But Wales questioned the call-up, saying Shingler was committed to them having represented Wales in an Under 20 international against France in March last year.

The IRB said in a statement Shingler's appearance in the Wales Under 20 team "indicated he was tied to Wales".