South Africa's electric wing Makazole Mapimpi scored two tries as the Springboks eased to a nine-try 57-3 win over neighbor Namibia, but it was a far from polished performance in the Rugby World Cup Pool B clash on Saturday.

Billed the "African Derby," there was only ever going to be one winner despite what Springboks coach Rassie Erasmus termed his "fringe" selection, and Namibia simply could not cope with the physicality of the South Africans.

Hooker Bongi Mbonambi (two), loose forwards Francois Louw, Schalk Brits and Siya Kolisi, fullback Warrick Gelant and center Lukhanyo Am also crossed for tries, but there was a lack of cohesion and, at times, quality that will worry Erasmus.

South Africa next faces Italy on Friday in Fukuroi, Shizuoka Prefecture, in a match that should decide second place in the pool, while Namibia faces the daunting prospect of New Zealand in Tokyo on Oct. 6.

The number of unforced errors made by the Boks, especially in the first half, was high and Elton Jantjies did little to suggest he is pushing Handre Pollard for a starting place at flyhalf with some poor decision-making and execution.

Not that skipper Brits saw much wrong in the performance.

"I'm really tired but it was a great performance by the boys, I'm really happy and it's a great game we're playing," he said after starting in an unfamiliar No. 8 role.

"I'll just play wherever the coach wants me to play. Just to be on the pitch with such a great bunch of guys is phenomenal"

Namibia, made up almost entirely of amateur players, never stopped trying to run the ball but did not manage a single line-break in the game.

South Africa produced four monstrous attacking scrums early on to highlight its dominance, referee Mathieu Raynal showing restraint as Namibia buckled and wheeled under the pressure.

The first three tries were all from rolling mauls following lineouts, two for Mbonambi and one by Louw, before Mapimpi secured the bonus point inside 27 minutes with a neat finish out wide.

Namibia flyhalf Cliven Loubser replied with a penalty before Am crossed to hand the Boks a 31-3 halftime lead.

They took almost 10 minutes to find their rhythm after the break but added a sixth try as Am sliced through a gap in the defense, Gelant finishing off.

Mapimpi crossed for his second out wide and then regular skipper Kolisi came off the bench to canter in, captain for the day Brits adding the ninth with 16 minutes remaining.

"For us, we're just trying to build on our momentum and today was a good test," Namibia skipper Tjiuee Uanivi said. "They played a great physical game and it's good to measure ourselves against that.

"We're just going to go back and look at the positives and negatives and fix that.

"It doesn't get any easier, eh? New Zealand move the ball quicker, an all-around good team and you can expect quality everywhere."