Cape Town - Cheetahs scrumhalf Ruan Pienaar has been placed on standby in case one of the three No 9's in the Springbok Rugby World Cup squad is ruled out with injury.

This was revealed by coach Rassie Erasmus on Friday as the Springboks trained at the Kobelco Steelers Rugby Club in Kobe.

Scrumhalf Herschel Jantjies (hamstring), wing Cheslin Kolbe (ankle) and flank Francois Louw (swollen knee) have injury niggles and did not train with the team.

Erasmus, however, told reporters he was confident that the trio would recover in time for next weekend's quarter-finals.

Jantjies has been the back-up scrumhalf to Faf de Klerk at the World Cup, with Cobus Reinach the other No 9 in the squad.

Erasmus said Jantjies picked up a light hamstring strain when he came on in Tuesday's 66-7 win over Canada.

"At this stage, it is precautionary but it's also one of those where we are a little bit nervous. We only have three scrumhalves here so we want to make sure that he rather has more recovery time. So, hopefully on Monday he is also ready to go."

In the worst case scenario, Erasmus said Pienaar would board a plane to Japan.

"I know Ruan Pienaar is currently playing very well back home. The difficult thing for the guys who were in our mix in South Africa is that there is no Currie Cup rugby now, whereas the PRO14 guys are actually playing now."

The 35-year-old Pienaar is vastly experienced, having played 88 Tests between 2006 and 2015, and was instrumental in the Cheetahs' recent Currie Cup triumph.

The coach added that Kolbe, who injured his ankle against Italy last Friday and missed the win over Canada, should be available for the quarter-finals.

"There's a very good chance - I'd say 80 to 90% - that he will be available (for the quarter-final)."

The Springboks will face either Japan, Ireland or Scotland in the quarter-finals.

- Compiled by Herman Mostert