Grant Gilchrist says best friend Stuart McInally has hit the jackpot with the Scotland captaincy six years after going all in as he gambled his career on a switch to hooker.

The Edinburgh forward was the shock choice to lead the Dark Blues into the World Cup after Gregor Townsend decided against handing former skippers Greig Laidlaw and John Barclay the armband.

But the appointment came as no surprise to club-mate Gilchrist, who has watched the 29-year-old risk everything by making a belated move from flanker to the front row aged 23.

Gilchrist has no doubt McInally could have enjoyed a more than decent career operating at the back of the pack.

But it was his transition to hooker than provided the springboard to the captaincy and Gilchrist says his pal is now reaping his just rewards.

He told the PA news agency: "The fact Rambo (McInally) moved position at a relatively older age is remarkable. He was on the bench for Scotland as a back-rower. He was more than good enough to play for Edinburgh 100 times as a back-rower.

"But to be brave enough to change position and take up a role that is so technical  it speaks volumes for the kind of professional he is.

"His line-out throwing is among the best in the world, yet he's a guy who had never thrown a line-out at the age of 23 or 24.

"That's remarkable but it's down to the fact he is so disciplined and hard-working and he thoroughly deserves to be named skipper.

"He sets an example to the whole squad and is always one of our best players on the pitch – that's what I look for in a captain."

McInally's path to becoming a Scotland regular and one of the world's best front-row operators in the loose has not always been smooth.

Gilchrist knows how tough it was for his friend to establish himself for club and country given the injury battle he had to overcome in the build-up to the 2015 World Cup, a tournament in which he eventually saw just 66 minutes action as his fitness woes struck again.

But the leadership qualities he first saw in McInally as a teenager shone through again as he battled his way to become Townsend's chief on-field lieutenant.

"Rambo has probably been one of my best mates over the last 10 years," said Gilchrist. "I met him playing for Scotland Under-18s, he was our captain then so I suppose you could say he's always been leadership material.

"He came through all the age groups with me and we broke into the Edinburgh first team at a similar time.

"We even went through tough spells in our career around the same period.  He was struggling to get a game and I was struggling for form coming back from my injury.

"He is such a professional and he works so hard that it was never a surprise to me that he would come through that spell. His game has just got better and better."

Scotland's Japanese campaign gets underway a week on Sunday with a massive clash against Ireland.

Joe Schmidt's men are the favourites heading into the Yokohama showdown but Gilchrist says his team are in the mood to cause an upset.

He said: "We're not going there to make up the numbers. We're going there to win games.

"Obviously we know how hard a challenge it is to win it but that is what we're aiming for.

"We know we'll need to perform well to get out of the pool but if we do, it's knock-out rugby from then on and who knows what could happen?"