Australia succumbed to a humbling innings defeat to South Africa, setting up a thrilling decider in Cape Town and adding to the questions hanging over Pat Cummins’ “Dad’s Army”.

On day five in Gqeberha, the unlikely hero was all-rounder Wiaan Mulder, who shattered Australian stumps three times.

The first broke a stubborn partnership of 69 from 27 overs between centurion Travis Head and nightwatchman Scott Boland, with Head playing on. The second and third came in short order after tea, with Boland’s resistance ended and captain Cummins bowled.

Before the break, Kagiso Rabada had won the latest instalment of his long battle with Steve Smith, who was caught pulling unwisely. He returned to the attack with clouds gathering to bowl Mitchell Starc, before Marco Jansen finished the job with the wicket of Josh Hazlewood.

This was a truly great South African victory, by an innings and 31 runs. They lost a bad toss, stuck in with poor weather that provided perfect bowling conditions on the first two days. They battled from 110 for six to post 425, thanks to Temba Bavuma’s captain’s knock.

Then they bowled Australia out twice inside 150 overs, despite an early injury to quick Anrich Nortje and more poor weather on the final day. In total, 145 overs were lost to weather, and the match was won deep in the final session.

But for Australia, the questions mount. They are in the foothills of an epic Test run that concludes with next summer’s Ashes. After the decider in Cape Town, they host New Zealand for four Tests and travel to India to five. Then they host England for a 150th anniversary of Test cricket celebration in Melbourne, before possibly competing in the World Test Championship final.

Here are some of those questions.

How do they ease their opener headache?

Australia made the extraordinary decision to recall Nic Maddinson to open in this series. Maddinson has been a fine Sheffield Shield player, but he is 34, and had not played Test cricket for a decade or a first-class match for 19 months because of a battle with cancer which required chemotherapy.

Maddinson made a 33-ball duck in his first innings back, and was thoroughly outclassed by Rabada in Gqeberha. At this stage, he does not look like even the short-term answer to Australia’s opening issues, which have lingered since the retirement of David Warner in 2024 and exacerbated by the departure of Usman Khawaja this year. At least Head batted well in the second innings, making his fourth ton as an opener and slowest in Test cricket since 2019.

Should they persist with Labuschagne?

Marnus Labuschagne, the No 3, is causing just as much of a headache. After a superb run in Test cricket from 2019 to 2022, he has now gone well over three years without a century. He was briefly dropped in the Caribbean last year, but fought his way back into the side, only to have the same issues. He was dismissed twice on day four, for 14 and 39, continuing a theme of the South Africa-born batsman getting in and getting out, often in brain-dead fashion. His second dismissal saw him try to hit Simon Harmer out of the park, into the wind, with the field set and Australia battling to save the game. He might get a stay of execution in Cape Town, but could have no complaints if he is dropped again.

Cameron Green as a specialist batsman?

Cameron Green has missed the first two Tests with injury, and is unlikely to be fit to play in Cape Town, but perhaps not bowl. He could come back for Labuschagne, or Beau Webster, the all-rounder who has fallen away somewhat after a promising start to his Test career.

Green made a century against Bangladesh in August, but remains an unfulfilled talent, and it is unclear whether he is a pure all-rounder who should bat at No 6 or 7, or a top-order batsman who bowls occasionally. The other option to come in as a batsman is Josh Inglis, the English-born keeper-bat. Matt Renshaw, brilliant from No 5 in the first Test, could move up the order.

Do they still need Lyon?

Veteran Nathan Lyon was left out in the second Test, the first time this has happened in a red-ball Test that he was fit for since 2013. David Warner was among those to question the decision. His replacement, Boland, was brilliant, as he so often is and Australia’s first-choice seamers might be ageing, but they are still immense.

Nevertheless, Australia did miss a spinner, and they might be reticent to leave him out in the coming months, which will necessitate another tough decision. Lyon is one month shy of his 39th birthday, and is playing so sporadically – and is often such a fringe player when he does – that it is hard to assess whether his powers are waning. He is their greatest offie, though.

Lyon is the emblem of an ageing side, nicknamed “Dad’s Army”. Every player is in his thirties, and they are heading for a cliff-edge together. Some regeneration is required, but exactly who is unclear.