Wales centre Jamie Roberts has called on the current side to vary their game when they take on a gargantuan Springboks outfit in the semi-final this weekend.

South Africa bullied Japan in the last-eight contest in Tokyo with their set-piece helping them claim a dominant 26-3 triumph over the Brave Blossoms.

Rassie Erasmus’ men will once again look to assert their authority up front on Sunday, although the Welsh should be far more resilient than the Japanese.

The two-time World Cup winners have bigger units in the pack, however, and Roberts, who garnered 94 caps for Warren Gatland’s team between 2008 and 2017, insists that they will have to expand their game and put pressure on wings Cheslin Kolbe and Makazole Mapimpi.

“They have to be innovative,” the centre told After The Whistle, a podcast hosted by World Cup winner Lewis Moody. “With South Africa and the second half they played against Japan, their control of possession and control of the advantage line was pretty special.

“One maul went about 40 metres so there are no prizes for guessing what Wales will be practising in training, which is defending driving mauls and scrums.

“If we try and beat South Africa at the scrum and lineouts, and try and arm-wrestle them, I think we will lose. We need to go and play, and we need to put pressure on the wider channels.

“I think the All Blacks showed in their opening match against the Springboks that they can expose their wingers. Yes, Kolbe and Mapimpi are good players attacking-wise, but I think defensively they’re a bit suspect, especially in the air.”

Both South Africa and Wales have often taken the conservative approach in this tournament but Roberts believes that the two teams will be pondering how to approach this encounter.

He said: “It’s going to be really intriguing how both sides approach that match. Do you roll the dice and try to get into those wider channels or do you potentially shoot yourself in the foot by doing so?

“I think they’ve (Wales) played a risk-averse brand of rugby. Yes, they’ve scored tries and they’ve put themselves in good positions, while they’ve also defended very well and tactically their kicking game has been spot on.

“The interesting thing for me about this semi-final against South Africa is that you’ve got two teams who play very similarly.

“The Springboks are very similar in that they don’t attack too much, they don’t play to width too much. They’re very direct and they rely on their pressure game in defence and they rely on their kicking game off their half-backs.”

Despite containing attacking threats behind the scrum, South Africa have played a tighter game than in the two years following the 2015 World Cup and Roberts praised their approach.

“This is the Boks’ strength and it’s great to see the Springboks go back to doing what the Springboks do best,” he added. “At the start of this World Cup cycle, they were probably a bit lost in the way they wanted to play the game.

“They tried a lot of different combinations and probably tried to play a little too much, and that’s not the Springboks. The best Springbok sides in the history of the game is set-piece orientated and big massive packs beating you up on the advantage line.

“But this is such an opportunity for Wales; will they ever get a better shot?”