Wales forward Ryan Jones admits he is wary of starting at lock against Scotland on Sunday.
Regular back-rower Jones has started only a few games in the second row for the Ospreys and once for Wales in the loss against the Barbarians in 2011.
Jones, 30, has been moved from blindside to lock as Bradley Davies is suspended and Dan Lydiate is fit.
"I'm a little bit nervous about it. I have yet to figure at this level as a [number] four," said Jones.
"It became a natural move having played some games at four this year [for the Ospreys]. It will be interesting to see how it goes but I'll go and give it my best shot."
With Davies having received a seven-week ban for his tip tackle on Donnacha Ryan in the Ireland game and Alun Wyn Jones and Luke Charteris both injured, Wales have gone for Ryan Jones to partner Ospreys team-mate Ian Evans.
"I've had bouts there, in and out and stuff, but I know what is required," insisted British and Irish Lion Jones.
"There is a lot of difference really [between back-row and lock].
"It's all based around a tighter game and the other thing it doesn't come instinctively to me yet because I haven't played there regularly. I don't train there regularly.
"I'm looking forward to the challenge really and hopefully it will go well."
On paper Jones, at 6ft 5in and usually a number eight or blinside flanker by trade, has a difficult brief up against Scotland's two locks Richie Gray and Jim Himilton, who are 6ft 9in and 6ft 8in respectively.
But Jones, who had an impressive game at flanker in the 23-21 win over Ireland in Dublin last Sunday, believes there is a lot more to the forward battle than just the line-out.
"They [Scotland] have got some big old guys, but rugby is for all shapes and sizes," said Jones, who captained Wales 27 times - just one behind the Wales record held by Ieuan Evans.
"There is a lot more to rugby than just the line-out and up there with those guys. There will be a lot of the game won and lost around the floor area.
"The set-piece notoriously gets better as the Championship goes on. The game has eveolved and there hasn't been a lot of set piece [in the opening weekend.
"[The line-out] will have an effect but I think the game will be won and lost in other areas.
"We have got to make sure we win out fair share of ball and make sure we utilise it well. It's always nice when you get up from a set-piece or a breakdown and backs are crossing gainlines.
"We have got some big old lumps out there [in the backs]."
Many are writing off Scotland's chances after they went down at home to England 13-6 last weekend, spurning a series of try chances.
But Jones refuses to suggest it will be an easy afternoon for Wales, who only just won their last home encounter to Scotland courtesy of a last-gasp try by wing Shane Williams.
"You can't afford to do that [write Scotland off] at this level. We know what the challenge is. We know each other inside out from the RaboDirect so there are a lot of personal battles fought on the weekend," insisted 59-times capped Jones.
"We can only worry about ourselves. We know they [Scotland] are going to be hurting and smarting from last weekend and coming down with a big point to prove."