Scotland vs South Africa: Finn Russell ruled out as Duncan Weir handed fly-half role for Springboks showdown

Blair Cowan also starts having been drafted into the squad as an injury replacement for Grant Gilchrist

Duncan Weir scores a try for Scotland against the USA (Getty Images)

Scotland's stand-in stand-off Duncan Weir insists he feels no pressure to live up to the standard set by injured colleague Finn Russell.

The Dark Blues' understudy playmaker has been handed the responsibility of making Vern Cotter's team excel in his Glasgow team-mate's absence.

Russell has been hobbling about on crutches since injuring his right ankle in Sunday's win over the United States and is not expected to resume training until the middle of next week.

The 23-year-old's confident swagger and inventive style have played a major part in the Scots' back-to-back bonus-point wins over Japan and the US.

But things will be ratcheted up a level as they now prepare to take on Pool B's top seeds South Africa on Saturday, when a win will book the Scots a slot in the knockout rounds.

However, Weir - who has had just 20 minutes of action so far - is ready to take on the two-time former winners in Newcastle.

Asked if he felt a responsibility to match Russell's levels of performance, Weir said: "I don't really think about that. I think about what I can bring as an individual. I think about what I can control. There's no point me thinking about outside factors like that.

"For me, it's about doing my job really well, making sure I boss the team and (am) really vocal in attack. Those things are all in my control and I'll just focus on that.

"I've been waiting on my chance and as soon as the squad for Saturday got announced I had to pinch myself - I'm going into St James' Park to start at a World Cup.

"I wouldn't say I feel pressure with what's at stake on Saturday - more excitement. We're one win away from a quarter-final with two games left.

"It's a huge achievement so far but it counts for nothing if we don't put in a performance this week and next."

Scrum-half Greig Laidlaw has formed an effective partnership with Russell since joining together 12 months ago - but he knows what it is like to link up with Weir and sees no reason to make major adjustments.

"I don't think I'll need to change anything," said the skipper. "Finn is a wonderful player but even though he's picked up a knock, he's played a lot of rugby as well so it's a good opportunity for 'Duncy' to come in.

"Early in the game it will be important for me to get him a few touches and settle him into his role. But Duncan has played enough rugby now to know what it's all about. He'll relish his chance."

Russell's absence, as well as that of flanker John Hardie following a head-knock, have been forced upon Cotter but the head coach has not held back from tinkering with his side again.

In what could be described as a makeshift line-up, the Kiwi has left several big-hitters on the bench - perhaps keeping one eye on next weekend's clash with Samoa which could ultimately decide the Scots' quarter-final hopes.

New arrival Blair Cowan - left out of the original 31-man squad - goes straight into the side at seven just days after replacing injured lock Grant Gilchrist.

Prop Gordon Reid starts his first match of the campaign in place of Ryan Grant, as does Richie Vernon, who comes in for Mark Bennett. While Bennett has been Scotland's star of the competition so far, Vernon will add might to the midfield in anticipation of the looming gain-line battle with the Boks.

Laidlaw returns at scrum-half, while wing Tommy Seymour starts in place of Sean Maitland. In the forwards hooker Fraser Brown gets his first start and is joined by WP Nel, who switches roles with Jon Welsh. Jonny Gray returns to start alongside brother Richie in place of Gilchrist.

The changes are completed by Josh Strauss, who moves to the blindside flank at the expense of Alasdair Strokosch to accommodate number eight David Denton.

Cotter rejected suggestions that his side had a second-string feel to it, saying: "This is our third game in 10 days. We've looked at workloads and potential injuries and there are players we feel that are better regenerating.

"These players will be giving 100 per cent of themselves and it is a team that will be competitive."

South Africa head coach Heyneke Meyer claimed earlier this week his side had been forced to change their line-out calls as they feared Afrikaners-turned-Scots Strauss and Nel would be able to crack their codes.

Both players trained with South Africa before committing themselves to Scotland but Cotter said: "I am sure their team evolves and changes every week so I am sure that while those two will be able to understand the exchanges between players I doubt they will know what's coming."

PA