Junior Springboks coach Dawie Theron has confirmed his starting line-up for the first of two matches against the Argentina Under-20 team in Santa Fe. Photo by Grant Pitcher/Gallo Images

Johannesburg - Blue Bulls under-21 hooker Arno van Wyk has joined the Junior Springboks in Auckland after a knee injury forced Malcolm Marx (Golden Lions) out of the IRB Junior World Championship.

Marx might be out of action for up to six weeks after he sustained the injury during a training session earlier in the week.

The burly front-rower became the second Junior Bok to be ruled out of the tournament after centre Rohan Janse van Rensburg returned home with an ankle injury.

Jean Luc du Preez, who picked up a nasty blow to the head against New Zealand's under-20s on Friday night, was released from hospital during the early hours of Saturday morning.

The flanker was carried off on a stretcher after receiving medical attention on the field. He was taken to a nearby hospital for examination and the scans revealed no damage.

Du Preez will now follow the IRB's Graduated Return to Play Protocol (GRTP).

There was more encouraging news for team coach, Dawie Theron, following a spate of injuries this week.

Centre Andre Esterhuizen and flank Jacques Vermeulen should return to training on Sunday after missing the New Zealand clash through injury.

Esterhuizen has completed his GRTP rehabilitation after leaving the field against Scotland following a bump to the head. Vermeulen hurt his ankle in the same match and also missed Friday's encounter.

“The NZ match is now behind us and we must plan carefully for Samoa, who will no doubt be a huge threat in Pukekohe,” Theron said on Saturday.

“Andre and Jacques will come into the selection picture, so I am glad we now have a few more options to choose from.”

South Africa, defending champions, England, and France are all unbeaten after two matches. Following the final pool fixtures, the three pool winners and the best placed second team will contest the semi-finals on June 15.