Australia's batsmen will be their own harshest critics after reaching 5-274 at stumps on day one of the series-deciding fourth Test in Brisbane, where India's unheralded attack exposed a lack of ruthlessness.

India's bowlers, boasting a combined 13 Test wickets at the toss, are believed to be the most inexperienced attack that Australia have confronted since 1880.

The tourists' injury crisis became bleaker with confirmation that spearhead Jasprit Bumrah (abdominal) and offspinner Ravichandran Ashwin (back) would be two of four enforced omissions.

India could have been excused for dropping their bundle when Navdeep Saini limped off during his eighth over, having suffered a groin injury that could prevent him from bowling again in the match.

Likewise when fellow paceman Shardul Thakur left the field in obvious discomfort late on Friday, having fumbled a return catch offered by Cameron Green on 19.

But the depleted visitors, as they have done throughout a four-Test series locked at 1-1, showed plenty of character in front of a sold-out and socially-distant crowd of 12,998.

David Warner and Marcus Harris both departed in the opening nine overs as Australia crashed to 2-17, while Steve Smith (36) and Matthew Wade (45) both failed to convert starts.

Labuschagne, who was dropped on 37 and 48, shook his head in disbelief after a mistimed pull shot resulted in a skied edge and his dismissal on 108.

It had otherwise been a textbook Gabba hundred from the leading run-scorer of the series, who worked hard early then cashed in as bowlers started to tire.

"Everybody gets judged harshly. But you are your own harshest critic," Labuschagne said.

"Everyone will look at their dismissals and go 'what could I have done better?'

"I'm definitely disappointed to not go on ... I have to make sure (in the second innings) I'm ready to get Australia into a position to win this Test.

"We still take the position we're in ... it was really nice to see Greeny and Tim (Paine) finish it off after we lost two quick wickets."

Debutant Washington Sundar, whose maiden Test scalp was former IPL teammate Smith, felt India did well to snare five wickets.

"It was really good for batting. The wicket was very good," Sundar said.

Green and Paine, unbeaten on 28 and 38 respectively, may yet fashion an imposing first-innings total.

But Paine, who opted to bat first on what he expected to be a "pretty good batting wicket for the first few days", would have loved nothing more than to sit in the dressing room throughout the day.

Such a scenario looked likely during the Labuschagne-Smith and Labuschagne-Wade stands, worth 70 and 113 runs respectively.

An all-run four in the first over after lunch signalled Labuschagne's intent, while another all-run four helped him reach three figures after a superb cover drive.

Labuschagne brought up his half-century in 145 balls, barely acknowledging the milestone, then only needed a further 50 deliveries to race to his first Test ton in a year.

Captain Ajinkya Rahane, having a grassed a regulation chance at gully offered by Labuschagne when Australia were 3-93, will be cursing three dropped catches.