Nic White will start at scrum half for the Wallabies on Saturday, two weeks after he disrupted the British & Irish Lions in what was supposed to be his last international.

White, 35, announced before the third Test in Sydney that the series finale would be his 73rd and final cap for Australia, and the squad donned mock moustaches in his honour for the pre-match photograph. It was supposed to be his final Wallabies appearance before he retired from the sport at the end of the year.

He irritated the Lions in pouring rain, inspiring a 22-12 win that deprived the tourists of a whitewash — but his farewell did not last long. An injury to Jake Gordon, who started the first two Lions Tests, meant that Joe Schmidt asked White to delay his retirement.

Five days after his goodbye he was back in Australia’s squad for the first two rounds of the Rugby Championship, and despite there being two other nines in the squad, he starts again, with James O’Connor as his half-back partner.

Tom Lynagh will not feature in South Africa as he recovers from the head injury caused by Dan Sheehan’s dangerous clearout. Schmidt has had to call upon an unexpected pairing of half backs, with O’Connor, also 35, wearing No10 on Saturday in his first international for three years.

Ben Donaldson, the back-up playmaker, is injured and so the Wallabies have no specialist fly-half cover. Tate McDermott and Andrew Kellaway are the replacement backs on a 6:2 bench. McDermott, a scrum half, had to play most of the second Lions Test on the wing because of an early injury to Harry Potter. The fly-half shortage means that White may even have to fulfil a new role on Saturday in the epilogue of his career. “Nic White can cover No10 and is astute enough to do so, Andrew Kellaway has the skill set as well if we go with what we’ve got at the moment,” Schmidt said.

Lynagh and Donaldson are the only absentees from the 23 that beat the Lions in Sydney. Taniela Tupou and Will Skelton, who so improved the Wallabies’ foundations, are fit to start.

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The Rugby Championship will offer late context to the Lions’ 2-1 series win. That result will be seen in an even more positive light if the Wallabies challenge the world champions over successive weekends in Johannesburg and Cape Town. Thumping defeats would have the opposite effect.

The Springboks, pioneers of the 7:1 split of replacement forwards to backs, went with the traditional 5:3 when Rassie Erasmus announced his team on Monday. However, Erasmus left open the possibility of bringing in RG Snyman as a sixth forward if the Wallabies opted for 6:2. He was not bound by Monday’s line-up as World Rugby regulation 15.1.2 stipulates that unions have until 48 hours before kick-off to announce and exchange their match-day squad.

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The most notable selection in the starting XV is Siya Kolisi at No8, a jersey he has never worn for the Springboks, to combat Fraser McReight at the breakdown. “On Siya, we actually changed our mind there,” Erasmus said. “The more we practised, the more we realised that the only position that the guy really plays at eight is at scrums, and that is 13 or 14 times during the game.”

South Africa beat the Barbarians, Italy (twice) and Georgia in their mid-year internationals. Their tactical innovations included setting up lineout pods for mauls in midfield, and a deliberate infringement at the kick-off to manufacture a scrum. World Rugby has since clarified that the kick-off tactic should have resulted in a penalty to Italy.

Argentina will host New Zealand in Córdoba and Buenos Aires on the first two weekends of the Rugby Championship. Following that, Argentina and South Africa travel to Australia and New Zealand respectively for two matches, before a final two-match block of New Zealand versus Australia home and away, and South Africa against Argentina in Durban and then Twickenham, on October 4.

The Rugby Championship

Saturday
South Africa v Australia (4.10pm)
Argentina v New Zealand (10.10pm)
TV Live on Sky Sports
Kick-off times BST