Australia are facing another Scott Boland conundrum after his terrific second-Test efforts made the Victorian almost impossible to leave out for Cape Town.

Much of the focus will be on the make up of Australia's batting for next week's series decider against South Africa, with three of the top-seven under the gun.

But not for the first time, Boland is at the centre of a tricky call.

He has played just 20 of 50 Tests since his iconic debut at the MCG in 2021-22, despite being fit for every match and averaging 18.44 with the ball.

But only once has he been picked ahead of Mitchell Starc, Pat Cummins or Josh Hazlewood, with that coming in the 2023 Ashes series opener.

But leaving him out next Tuesday against South Africa would perhaps be the cruellest call made yet against the ever dependable 37-year-old.

Boland ran through South Africa's top-order across the opening three days in Gqeberha with 5-81, including four of the first five wickets.

A 166-ball nightwatchman stay then threatened to save the Test on day five, with only Travis Head (117) having a longer knock for Australia in the innings-and-31-run loss. 

Australia will wait until they train in Cape Town on Saturday before looking at the wicket and deciding if a spinner is called for, with Nathan Lyon to return if so.

That would leave Boland, Starc, Hazlewood and captain Cummins fighting over three spots, assuming the quartet all pull up well.

"I don't think he can do much more," Cummins said. 

"Five-fer, pick of the bowls. How gritty he was with his batting innings. He even put his hand up on day three to go in nightwatchman after he'd just bowled 20 overs. 

"I couldn't love that bloke any more, he's such a champion. 

"We'll get to Cape Town, we'll have a look see how everyone pulls up - but he had a fantastic week."

Cummins also stood by the decision not to play Lyon at St George's Park, on a green pitch, under grey skies and in wet conditions on the opening few days.

Hazlewood's food poisoning complicated the situation as South Africa recovered to post 9-425 declared.

That left Beau Webster bowling more than expected, while Matt Renshaw, Nic Maddinson and Marnus Labuschagne all sent down spin.

"I don't think it's any secret that he's not too happy when he's not playing," Cummins said of Lyon.

"But I think he understands. He was great, he's a big boy, he accepts it and it's 'no worries', he moves on and turns into the great team man that he is this week.

"Every game you're trying to pick five or six bowlers in four slots, all who are known match-winners who have been fantastic. 

"We'll get to Cape Town and talk about conditions, how people are tracking, and how the game's going to pan out.

"And like every Test, his name will be front and centre."