Sharks prop Lourens Adriaanse has been called up to the Springbok squad after Trevor Nyakane was ruled out because of an ankle injury.

Nyakane will miss South Africa's first two matches of the Rugby Championship against Argentina. He will continue his rehabilitation under the supervision of both the Bulls and Springboks' medical and conditioning team.

Sharks prop Adriaanse will join the Springbok squad in Sandton on Monday. The Springbok training squad has started to assemble in stages for their preparation of the Rugby Championship match against the Pumas on Saturday, 20 August in Nelspruit.

The locally-based contingent of the squad assembled on Sunday in Sandton while the nine Lions players are expected at the camp Thursday. The overseas-based players and the squad's two Olympians will join up with the rest of the players on Sunday, 14 August.

Springbok coach Allister Coetzee said although Nyakane was making good progress he would not be available for selection for the opening two rounds.

"Trevor will continue with his medical treatment, conditioning and recovery but we obviously need to get a replacement in for the two weeks, or as soon as Trevor is declared fit. It will be a risk not to have five fit props in the squad," said Coetzee.

"Like Trevor, Lourens can play on both sides of the scrum and he was on our standby list. Other prop candidates such as Jannie du Plessis, Lizo Gqoboka and Coenie Oosthuizen are all injured and therefore not available."

Adriaanse made his only appearance to date for the Boks on 23 November 2013 against France in Paris, aged 25.