Springboks head coach Jacques Nienaber will be emotional and scrum-half Grant Williams hopeful when South Africa confront Argentina on Saturday in a Rugby Championship final-round match.The match in Johannesburg will be the final Test at home for the South Africans before three warm-up games prepare them to defend the Rugby World Cup title in France from September 10.”It will be a bit emotional on Saturday,” admitted media-shy Nienaber as the clash with the Pumas will be his last international on home soil before leaving his post after the global showpiece.Nienaber, who succeeded World Cup-winning coach Rassie Erasmus in 2020, is joining Irish giants Leinster following the World Cup.After almost two decades working with Erasmus, the expert in defence tactics had his personal moment of glory by leading the Springboks to a 2021 series win over the British and Irish Lions.”Beating the Lions after losing the first Test was special, but the ultimate dream is lifting the World Cup trophy,” says Nienaber.”At one stage my ambition was to be a physiotherapist in Bloemfontein. Now I am head coach of a wonderful team. They make me so happy.”Nienaber works closely with South Africa director of rugby Erasmus, continuing a partnership that began in 2005 and included spells with the Stormers and Munster.”Rassie and I have always worked as a team. I pick his brains all the time,” he said of Erasmus, who transformed the Springboks from a laughing stock in 2017 to world champions within two years.Among nine changes Nienaber made to a starting line-up well beaten in New Zealand in mid July was giving Williams his first start after three appearances off the bench.Five scrum-halves – Williams, Faf de Klerk, Cobus Reinach, Jaden Hendrikse and Herschel Jantjies — are contesting three places in a World Cup squad to be named on August 8.De Klerk is a certainty and Jantjies, the second choice in Japan four years ago, is unlikely to make it this time.   – Trump card -Williams, who plays for the Sharks in Durban, can also operate on the wing and this versatility could be a trump card, provided he performs well at Ellis Park. “Grant gave his all, even when he was well down the scrum-half pecking order. He deserves this opportunity having repeatedly put his hand up,” said Nienaber. Razor-sharp Williams will form a new half-back partnership with fly-half Manie Libbok while Auckland starters De Klerk and Damian Willemse drop to the bench.Libbok also has much to play for with first choice Handre Pollard, who kicked 22 points in the 2019 World Cup final triumph over England, sidelined by a calf injury.World Cup-winning captain Siya Kolisi will be another absentee on Saturday, due to a knee injury, but Nienaber hopes he will be available for an August 19 warm-up against Wales. Another significant change is at hooker with Malcolm Marx starting and Bongi Mbonambi on the bench in a reversal of their usual roles.”Bongi has had more Test exposure than Malcolm and we do not want to start our World Cup campaign with some guys having the majority of the build-up game time,” said Nienaber.”There will always be injuries and, if one player dominates a position, we could be forced to bring in someone who will be ‘cold’ because he has had limited time on the pitch.” The match in a Championship reduced from two rounds to one because of the World Cup may be a dead rubber as New Zealand will seal top spot earlier on Saturday even with a draw in Australia. Defending champions New Zealand have nine points, South Africa five, Argentina four and Australia just one.Argentina have a poor record in Johannesburg, conceding 182 points in three losses, but coach Michael Cheika is hopeful after a last-gasp victory in Australia two weekends ago.”There was some ill discipline and bad decisions in Sydney, but I am confident we will show improvement against the world champions,” said the Australian.