Tim Paine has been backed to captain Australia until at least a possible World Test Championship final appearance in 2021 after leading the team from the fallout of the Newlands ball-tampering scandal to the brink of a clean sweep of this season's Tests following the retention of the Ashes last year.

Paine produced one of his most influence performances in Melbourne, scoring a momentum-seizing 79 in Australia's first innings and then claiming eight dismissals in a faultless performance with the gloves including a superb stumping to remove Henry Nicholls.

The Sydney Test which starts on Friday marks the last in which Steven Smith is not eligible to be Australia captain, with his leadership ban finishing at the end of March, although his has not been the only name associated with taking the armband when it does move on from Paine, with Pat Cummins' credentials continuing to grow.

Australia's next Test assignment is a two-match series in Bangladesh in June before the 2020-21 season which includes the heavyweight four-match contest against India. Australia and India are currently strongly placed to be in the Test Championship final at Lord's in mid-2021 with head coach Justin Langer seeing no reason why Paine - who he termed "almost our most important player" - can't be the man in charge should that come to fruition.

"Truthfully, I can't see one reason why he wouldn't," Langer said. "His last game - you judge on his last performance - he was probably pushing to be Man of the Match. He had eight eight dismissals, 70-odd with the bat, and the way he played his innings was what was most exciting. The way he leads the group. I just literally can't think of one reason at the moment, he's so fit, as to why he wouldn't keep playing for as long as he wants to or needs to."

Retaining the Ashes in England - something Australia had not done since 2001 - was a hugely significant achievement for a team that had been through huge turmoil in the preceding year. However, at the start of the home season, there was a sense of uncertainty about what would happen next year - partly due to Smith's availability as captain from March 2020 and also a perception that Alex Carey is making a strong case to be part of the Test team - but any questions about the medium-term leadership now appear to have been put to bed.

"The truth is there's been conjecture from outside, there's never been one millisecond of conjecture from within our team," Langer said. "I said at the start of the summer, he's almost our most important player, because he's a very good leader, his captaincy is excellent, he's the best wicketkeeper in the world, he's as fit as anyone in the group and we knew that if he believed he could bat as well as we think we can then you'll see results like we did in the last Test and at times during the Ashes.

"There's always a bit of conjecture, but certainly not within our camp. I hope he plays for as long as he possibly can because his leadership has been brilliant, working with the leadership group, I love working with him."

Langer acknowledged the stark contrast between where the team sits now and a year ago when they entered the Sydney Test against India under huge scrutiny following defeat in Melbourne, and they would go on to be taken for over 600 across the first two days of the Test and be made to follow on before rain forced a draw.

"The feeling in the camp is unbelievable but the trick is to maintain it," Langer said. "The Australian cricket team in the past has been able to do [that], hopefully I can be sitting here in 12 months' time again with a smile on my face… continue building this great momentum that's happening in Australian cricket at the moment. It didn't feel like it 12 months ago."

The immediate aim for Paine and Langer is to secure victory at the SCG, which would give Australia their first sweep of a home summer since 2013-14. The selection decision to be made is whether to find a place for the uncapped legspinner Mitchell Swepson on a surface that is expected to take turn, but two days out the likelier route was for an unchanged team with some additional workload for Marnus Labuschagne.

"It's certainly an option," Langer said. "That's how we have to look at it - we're talking about finding another allrounder in Australian cricket - well it might give us an opportunity to bowl Marnus and Travis Head a few overs, to find those extra overs we're looking for.

"Every time Marnus gets the ball in his hand, it's pretty exciting. He's working hard on getting his lines right, so he makes them play a bit more, but he's an exciting prospect, the way he spins the ball, and the more he can bowl in games that's important.

"It will be hard to make changes, that said I think it's really important that we wait because we've seen it in the Shield games and the groundsman is telling us he's expecting it to spin, so we have to respect that. We'll wait and see over the next two days what the wicket looks like."

Josh Hazlewood was back bowling in the nets on Wednesday as he recovers from the hamstring injury he sustained in Perth but is set to return to action through the BBL before the one-day tour of India.