'Most important player': Justin Langer's huge confession in Aussie captaincy debate

Justin Langer has backed Tim Paine to continue as captain until at least 2021, when Australia hope to contest the inaugural world Test championship final at Lord's.

Debate about Paine's captaincy has flowed thick and fast from the moment he assumed the title in the wreckage of the sandpaper scandal in 2018.

Steve Smith's leadership ban expires in March.

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Many pundits had subscribed to the theory that Paine was merely warming the hot seat until his predecessor Smith reclaimed the captaincy.

But Langer has emphatically backed Paine to continue to lead until the Test championship final in mid-2021, showering the 35-year-old with praise after his knock of 79 in the Boxing Day Test.

"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," Langer told reporters.

"He's as fit as anyone in the group and we knew that if he believed he could bat - as well as we think he can - then you'll see results like we did in the last Test and at times during the Ashes.

"You judge on his last performance, he was probably pushing to be man of the match.

"I just literally can't think of one reason at the moment ... as to why he wouldn't (be captain come 2021 and) keep playing for as long as he wants to or needs to."

Langer, Paine and Smith have all batted away questions regarding the captaincy over the past year, as have Cricket Australia chief executive Kevin Roberts and chairman Earl Eddings.

"The truth is there's been conjecture from outside, there's never been one millisecond of conjecture from within," Langer said.

"I hope he plays for as long as he possibly can because his leadership has been brilliant ... I love working with him."

Aussies eyeing Test championship final

Australia are currently second on the International Cricket Council's Test championship table.

Points are up for grabs in every Test, with the top two sides in 2021 to square off at the home of cricket.

Langer suggested Paine and his fellow leaders identified that final as their next big goal at the start of the home summer.

"I put it to the team at the start of this summer - what's our next target? - put it to the leadership group and they started talking about the world Test championship," he said.

"There's a focus there. We have a bit of a target."