The first name on South Africa's team sheet for Saturday's engagement with Scotland at Murrayfield? Beast. Beast Mtawarira. They like to print their line up from 1 to 15, the Springboks, and the No 1 position – that of loosehead prop – has become occupied by the imposing 6ft 2in, 18st 2lb unit who started his life back in his native in Zimbabwe as Tendai Mtawarira. Not that you will find any mention of his actual first name on the paperwork carried by the world champions on their end-of-year tour.

So when did he become the Beast, the 23-year-old who has come to fill the gargantuan Springbok void left by the man known as 'the Ox', the mountainous Jacobus Petrus – 'Os'– du Randt? "I've had it for a long time," Mtawarira replied, with a deep bass voice somewhere down in the Barry White region. "I've had it since I was nine years old. It's something that's stuck. It was my school-mates who gave me it."

It had something to do with him being "a bit of a bully" in his primary school days in Harare, Mtawarira confessed. It was back then, when his huge frame was knocking down smaller contemporaries in a football match, that a local rugby coach thought he might be better suited to the rough and tumble of the 15-man game. It has only been in the past two years, though, that Mtawarira has made a name for himself as a beast of a prop.

A fearsome scrummager and battering ram ball carrier, he started to emerge as a talismanic figure with the Sharks in the Super 14 competition last season. Since his debut appearance for South Africa against Wales in Pretoria in June, the Springbok crowd have come to mimic the chant that has become familiar whenever he gets the ball in 'the Shark Tank', the old Kings Park Stadium in Durban: "Beast! Beast! Beast!" He says: "I don't really hear much when I'm on the field. I get told about it after the game, that they were chanting my name. It is special."

The same could be said of the Beast, who has swiftly established himself not just as a cult figure in South Africa but also as the natural successor to the Ox as the Springboks' first-choice loosehead. Du Randt won his 80th and last cap as a World Cup final winner against England in Paris in October last year. It was his second taste of success in the Webb Ellis Cup, having been in the Springbok side that lifted it on home soil in 1995. A Bloemfontein farmer, he was drawn from rather different African stock than Mtawarira, who played for Zimbabwe at schools level and who (like Brian Mujati, the fellow prop who will be on the replacements' bench at Murrayfield) qualified for South Africa on residency grounds.

It was while playing as a No 8 for Peterhouse School south of Harare that Mtawarira was spotted by the Sharks and invited to become a member of their academy set-up in Durban. His conversion to prop only came in 2006 and yet now, after an excellent Tri Nations season and eight caps in all, he has become a cornerstone of the Springboks' front row. "It's a huge honour to be in the team and in the No1 jersey," he reflected, sitting on the first floor of an Edinburgh hotel, looking out to the Royal Mile. "I definitely want to play my part. All the guys in the pack are behind me. And, of course, Bismarck and John are next to me, so I'm ready for anything."

Yes, Bismarck and the Beast – these are changed times for the Boks down at the coal face. Against England in the World Cup final 13 months ago they had the seasoned trio of Du Randt at loosehead, John Smit at hooker and CJ van der Linde at tighthead. Against Scotland on Saturday, Mtawarira will be packing down at loosehead, with Bismarck du Plessis at hooker and Smit in the unfamiliar realm of tighthead. For Smit, who equals Du Randt's Springbok forwards' record cap haul of 80, it will be a second successive appearance in the No 3 jersey, having filled it in the 20-15 victory against Wales in Cardiff last Saturday.

"Last weekend showed that John can play tighthead," Mtawarira said of the Springbok captain. "He's doing very well. We're doing a lot of work together. Just today we had a very good scrumming session. We've got to take that confidence on to the field against Scotland."

South Africa might still be striving for a measure of consistency under their coach of 11 months, Peter de Villiers, but even after taking their foot off the pedal with 30 minutes remaining in Cardiff they still managed to shut out the Welsh on the try front. At Murrayfield they will be facing a Scotland team who have failed to score a try at home for 14 months. Still, Mtawarira in particular could be in for a difficult afternoon in the west end of Edinburgh on Saturday.

The stand out performer for the Scots in their 32-6 defeat against a shadow All Blacks side last Saturday was the man who will be Mtawarira's direct opponent. Euan Murray, Scotland's tighthead prop, gave a torrid time to Jamie Mackintosh, the 6ft 5in, 20st 6lb giant who was making his debut at loosehead for New Zealand. Mtawarira is likely to provide a more thorough examination of the 28-year-old Scot's credentials as a potential British and Irish Lion.

"Their loosehead..." Murray had pondered, across the Scottish capital at Murrayfield, earlier in the day. "I don't even know what his real name is, but he has a reputation for dismantling tightheads." Someone suggested it might be billed as Beauty and the Beast. The thought clearly tickled Murray, a beast of a size himself at 6ft 1in and 18st 9lb.

Certainly, it promises to be an intriguing battle-within-a-battle: the Beast and the Northampton Saint. Murray is a thoughtful, quietly-spoken character. He happens to be an accomplished piano player among the piano-shifters and a qualified vet too. He is also deeply religious, his Christian faith having been strengthened by the episode that almost led to the curtailment of his rugby career – the seizure he suffered while playing for Glasgow against Munster three years ago.

The day after a shift on the international scene, Murray likes to "go to church and have a sleep." He is expecting a particularly punishing 80 minutes on Saturday. "The Springboks are the most physical team I've played against," he said. "They've got the biggest, strongest, fastest forwards. They're very abrasive, very direct. With New Zealand, there's probably more stepping and stuff, more changing of direction. The South Africans just run at you like trains."

It remains to be seen if Murray and his team-mates can put a few autumn leaves on the Murrayfield line. Mtawarira, for one, remains wary of them. "The Scottish pack did very well against the All Blacks," he said. "They caused them problems. Euan Murray's a good tighthead. He'll be a big challenge, definitely. I look forward to taking him on."

Then, when the Murrayfield match is over, and it comes to booking a table for dinner, what name might South Africa's new prop idol be using. The enquiry drew a hearty laugh. "I call myself Mr Beast," the No 1 Springbok proclaimed.

The Beast's credentials:
Date of birth: 08-01-1985
Weight: 115 Kg
Position: Prop
Height: 188 cm
Born: Harare, Zimbabwe
Club: Natal Sharks