South Africa coach Rassie Erasmus was delighted to get 50 minutes from regular skipper Siya Kolisi in Saturday's 24-18 Rugby World Cup warm-up win over Argentina at Loftus Versfeld.

Kolisi, the Boks' first black test captain and a key figure for the side on and off the pitch, missed the entire international season with a knee injury but was able to prove his fitness with a solid display against the physical South Americans.

"Siya was wonderful," Erasmus told reporters. "We wanted to get him off after 30 minutes but he said was feeling great. At halftime I asked him if he wanted to go more, and he said he wanted 70 minutes!"

Erasmus confirmed Kolisi was feeling no ill-effects from the bruising contest and that now the challenge was to bring him up to full match fitness after just two starts in provincial and international rugby since May.

"Medically he is fine and that's great. Next is to condition him physically with match fitness and we will give him more game-time in the Japan match to get him ready.

"We are fast-tracking Siya because we know what we have in him and he is our captain."

Kolisi will get a final run-out ahead of the Springboks’ World Cup opener against New Zealand in Yokohama on Sept. 21 with a meeting against hosts Japan two weeks prior to that.

Erasmus rested 18 players for the contest in Pretoria, with a completely new starting XV from the side that beat Argentina 46-13 in Salta the week before to lift the Rugby Championship.

He said he knew that would make it harder to win but said it was necessary to cast his eye over a few players who still needed to prove that they should be on the plane to Japan.

"I won’t name names but there were one or two we had to get confirmation on and I had some doubts," he said.

"We will now take 37 guys to Bloemfontein tomorrow (Sunday) and will be there until Wednesday. Then the guys will go home until Sunday, before we return to Jo’burg for the squad announcement on Aug. 26.

"I can say we got confirmation of some things tonight. To rest 18 players … I know people don’t like manoeuvring around Bok teams and if we had lost, you guys (the media) would have got into me, but then again you learn so much."