De Villiers and Steyn teamed up in the opening two Tests of the recent series against England but Steyn missed the last contest in Port Elizabeth because he was getting married and was replaced by Wynand Olivier.

"Wynand played well in that match but Frans is such a world class player that he has to make a difference when he is present," said De Villiers.

"He brings a lot to the team.

"I felt that if Frans was available to play for the Sharks in Super Rugby's knock-out stages he would have brought a lot to them. He is a fantastic player and he is looking strong and fit," added the captain.

De Villiers also backed Bok fly-half Morne Steyn to do well during the tournament and disagreed with the view that the Bulls number 10 was out of form against England.

"I don't agree that he was out of form against England," he said.

"I think his general play was good.

"His goal-kicking did let him down. He was not as good in that department as he usually is and people have high expectations of him.

"But his decision-making was excellent and a few of the tries we scored were down to him," added De Villiers.

The 75 Test veteran also revealed that although Argentina were newcomers to the annual competition between the leading southern hemisphere nations, the Springboks will not underestimate them, especially in the opening Test in Cape Town on August 18.

"I don't think playing Argentina will be easy," he explained.

"We view the matches against them as very important as it could play an important role in determining the eventual winners of the tournament.

"The history of SA versus Argentina is pretty impressive and we're playing at a historic venue like Newlands, which is steeped in tradition.

"Argentina have great skill and have big forwards, all of which makes for a great match.

"You can expect Argentina to be psyched up for the occasion," he added.