Pretoria - Springbok head coach Rassie Erasmus said on Saturday 2018 World Rugby Breakthrough Player of the Year Aphiwe Dyantyi is set to miss the World Cup in Japan due to injury.

The winger, former Springboks skipper Warren Whiteley and highly-rated utility back Damian Willemse are unlikely to be included in the 31-man squad for the September 20-November 2 global showpiece.

"Injured players like Dyantyi, Whiteley and Willemse are in a race against time due to bad luck," he said after South Africa beat Argentina 24-18 in a World Cup warm-up Test in Pretoria.

"They are all world-class players but they have not really played a lot this year which is why it is going to be tough for them just to hop up to the top level."

However, there was good news from Erasmus for some contenders, including winger Sibusiso Nkosi, who scored two brilliant tries against the Pumas, and regular skipper and loose forward Siya Kolisi.

The coach said Nkosi, Kolisi, scrumhalves Faf de Klerk, Herschel Jantjies and Cobus Reinach, locks Eben Etzebeth, Franco Mostert, RG Snyman and Lood de Jager and hookers Malcolm Marx, Bongi Mbonambi and Schalk Brits would go to Japan.

"We wanted 30 minutes from Siya, but he said he felt great so we let him continue. Although he really struggled after 50 minutes, he is medically fine.

"He just needs to get match fit and we will work hard on his conditioning and give him a lot of game time in our warm-up game against Japan.

"We are fast-tracking him in a big way because he is our captain, so it is a special case," Erasmus stressed.

Kolisi was injured in May playing in Super Rugby and the warm-up against Argentina was his first Springboks appearance since last November in Wales.

"It was not a great performance today, but it was gutsy, and the guys all tried hard. The most difficult thing now is to pick 31 for the World Cup and some guys are going to be heartbroken.

"We took a chance and rested 18 players, so you can draw conclusions from that about the make-up of the squad. I would have been gutted to lose tonight.

"The team we put together had a lot of different combinations, which is why it was a stop-start game.

"Argentina are also a very disruptive team so, with our lack of combinations, it was a bit of a perfect storm.

"But we also gave away too many penalties, which made it a grind. It was frustrating because we made it hard for ourselves," Erasmus said.

South Africa are in Pool B at the World Cup with defending champions New Zealand, Canada, Italy and Namibia while Argentina will face England, France, Tonga and the United States in Pool C.