Captain Pat Cummins has flown back to Sydney due to a serious family illness after Australia's second Test capitulation in Delhi.

Cummins is expected to return to India later in the week as a demoralised Australia try to regroup for the third Test in Indore, starting on March 1.

Although the fast bowler is not expected to miss a Test, vice-captain Steve Smith could lead the team instead of Cummins if required.

Smith last filled in for Cummins during the Adelaide day-night Test against West Indies in December.

"We've got some strong leaders around the group," Australia coach Andrew McDonald said on Monday.

"We'll be in contact with Patty as well, we've got some decisions to make around squads and injuries.

"He'll still be engaged with what's happening back home but we've got some strong leaders in the squad who will be able to pick up the slack on the ground."

Cummins was Australia's only recognised fast bowler in Delhi after the tourists elected to give Matt Kuhnemann a debut to play as a third spinner alongside Nathan Lyon and Todd Murphy.

Fellow star quick Mitchell Starc is in line to return for the third Test but Josh Hazlewood will soon leave the squad and head back to Australia after battling an achilles injury early in the tour.

Scott Boland featured alongside Cummins in the series opener in Nagpur, but the popular Victorian was dropped for Kuhnemann.

Important allrounder Cameron Green will almost certainly return for the third Test after recovering from a broken finger suffered against South Africa in December.

Green will slot straight back in at No.6, likely in place of an out-of-sorts Matt Renshaw, to give Australia another genuine pace option.

McDonald said he was comfortable with players taking a break ahead of the third Test if that is what they needed.

"The ability to go away, freshen up - and they're not going to switch off totally, they're going to be thinking about exactly what happened, they're going to be running through it in their heads," McDonald said.

"When we come back together, hopefully by that space within the group we've got a bit more clarity and we can push forward.

"We feel as though some players need a break to mentally freshen up and if we flatten them too early in the series, I think a flat player on tour, we've seen how they perform over the years.

"It's about finding that balance. People are well within their rights to critique what we do, that's their opinion and we respect their opinion.

On Sunday, Cummins admitted Australia went "too high tempo" as they lost the second Test in Delhi inside three days.

Australia's hopes of winning a Test series in India for the first time in 19 years were ended in less than six days of cricket, crushed twice by a ruthless Indian spin attack.

While they were never in the contest in the opening Test in Nagpur, at Arjun Jaitley Stadium the tourists began day three with the advantage but were demoralised by tea.

Australia's collapse of 9-48 was their third-worst in the third innings of a Test, behind the infamous Cape Town debacle of 2011 (9-36) and a match against the World XI in 2005 (9-47) when the country's golden generation were already in a winning position.