Cape Town - Springbok coach Rassie Erasmus is happy the gamble on captain Siya Kolisi's fitness paid off.

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There was an injury cloud over Kolisi's head in the build-up to the 2019 Rugby World Cup in Japan.

Kolisi had suffered a knee injury in the latter stages of Super Rugby and the injury ruled him out of the Springboks' winning Rugby Championship campaign.

He made a return for Western Province in the Currie Cup, before playing for South Africa in the friendly Test against Argentina in Pretoria on August 17.

Kolisi proved his fitness just in time for the team's departure to Japan and then grew from strength to strength as he led the Springboks to World Cup glory.

Erasmus, speaking at OR Tambo International Airport in Johannesburg on Tuesday after the Boks arrived back in the country, said Kolisi's fitness was the only major injury worry. 

"We decided that when we got on to that plane to Japan all 31 players must be fit and ready to train. Out of the 40-odd training sessions we had over there, there were probably three where we had players sitting out with niggling injuries and Siya was one of them," Erasmus said.

"The only guy we really took a chance with was Siya. We had to manage him and his whole load and how we were going to make him play."

The coach added Kolisi's presence was vital in Japan.

"For us to have him there was really important, firstly because he is a great rugby player and secondly because he is our captain.

"I thought his form wasn't great in the first two games and that's why we subbed him early until he got fully fit. In the last three games his form was absolutely outstanding."