"I'VE never been naturally gifted at running," says Alex Dunbar.

It is a casual remark, but on reflection it should be taken with the same pinch of salt you would have to reach for if David Hockney told you that painting was never really his thing or Michel Roux claimed he was always pretty clueless in the kitchen.

For one thing, Dunbar's line of work as an international centre demands a certain aptitude at the old running business. And for another, it is a matter of record that no Scottish back has covered the ground faster than he did in Rome's Stadio Olimpico last year when he hit 33.8 km/h (or just over 21mph) as he ran away to score the first of his two tries against Italy.

Granted, Eric Liddell, Derek Stark and other noted Scottish speedsters of the past never played with GPS devices strapped between their shoulder blades, but even if Dunbar's achievement must be qualified with the words "since records began" the fact remains that he is pretty nifty when he wants to be.

And yet, Dunbar has a point in deflecting the suggestion that he might be Murrayfield's answer to Usain Bolt. For while it is certainly true that he can shift a bit, his greatest value to Scotland at the moment lies in his talent for stopping opponents from doing the same. Over the past two Six Nations matches, Dunbar has emerged as one of the most effective tacklers in the modern game - gifted not just in getting players to the ground but snaffling the ball away as well.

The most obvious reference point would be Brian O'Driscoll. While other tacklers were still lying on the floor feeling proud of themselves, O'Driscoll would be back on his feet, ripping possession away and probably launching a devastating counter-attack for good measure. Dunbar acknowledges the Irishman's game-changing (in every way) contribution to the art, but he considers that the All Blacks, pretty much to a man, have it nailed down as well.

"When you watch New Zealand and a few other teams that play that way, they bounce back to the feet," he says. "There is constantly someone on the ball. If we can do that then hopefully teams will tire because they have to pile in with an extra two or three guys.

"It is something I've worked on. Matt Taylor [the Glasgow and Scotland defence coach] has put a real emphasis on defence and has worked hard with the Glasgow boys in the last two years. The way rugby's going just now, on the back of turnovers and mistakes it's a real opportunity to score. Defences are getting so much better you've almost got to create errors in their attack to create chances to score by putting them under pressure."

Bear in mind we are not talking about nicking sweeties off gullible weans here. In Scotland's first game this year, Dunbar's midfield opponents were Wesley Fofana and Mathieu Bastareaud. In the second he was up against Jamie Roberts and Jonathan Davies. And next on the Six Nations bill he gets up close and personal with Andrea Masi and Luca Morisi, the likely centres for Italy against Scotland at Murrayfield next weekend.

And don't fall into the "It's only Italy" trap. Masi was the Six Nations player of the Championship in 2011, while Morisi helped himself to two tries against England last weekend. The Azzurri's performance at Twickenham showed a cutting edge that caught Stuart Lancaster's side on the hop, although their defensive lapses in the later stages suggests they still lack staying power at this level.

Will there be opportunities, then, for Scotland's strike runners in the final quarter next weekend? Dunbar collected that brace against Italy last year, but as befits a man with a farming background - he completed an HNC in agriculture before turning to full-time rugby - he is more usually seen as the muck-shoveller in the Scotland backline these days. By contrast, his fellow centre Mark Bennett is typically cast as the creative genius of their midfield partnership, although Dunbar would be entitled to point out that the four tries he has scored for his country are four more than Bennett has delivered to date.

Does he resent the caricature, or even just the suggestion that he is living in Bennett's shadow? Not hugely. "It doesn't really bother me," he shrugs. "If the team's playing well and creating good opportunities and winning, that's the main thing. So it doesn't bother me that I'm not scoring, not making 20, 30-metre breaks and all that stuff so long as the team's playing well. You enjoy it so much more when you're playing well and you end up winning."

Which is, of course, something Scotland haven't yet cracked in this year's championship. Winning has become a habit for Dunbar when he dons his Glasgow Warriors shirt, but it has been frustratingly elusive for the 24-year-old on Test duty. In total, he has played 13 times for his country and found himself on the winning side on only four occasions. His Six Nations record reads: played seven, lost six. Yet, he is anything but downcast by how things have gone in this year's losses to France and Wales.

"Obviously, any rugby player wants to win all the time and if you don't get the win then you are obviously hugely frustrated. But we'd be more upset if we weren't creating chances. I think we've created a lot of chances and we've been in a position to win, but it's just concentration in the breakdown, and little areas. One or two events in the game can change the whole aspect of the game and very quickly turn them into wins."

The bookies overwhelmingly favour Scotland next weekend. Since Italy's admission to the Six Nations in 2000, Scotland have lost the fixture six times, including that gruesome Murrayfield afternoon in 2007 when they shipped three tries in the opening six minutes. Italy made another impressively fast start at Twickenham last weekend, when Sergio Parisse scored the first of their tries after three minutes, so Dunbar is adamant that it is up to Scotland to take the initiative this time.

"We can't relax and think it's just going to happen," he says. "We need to really fire into them, put them under a lot of pressure and hopefully build off the back of their mistakes and score some tries."