Indian captain Jasprit Bumrah in fitness race against Australia

Heading into the biggest day of this five-Test series, huge doubts remain over India’s captain and most important strike bowler.

All eyes will be on Jasprit Bumrah on Sunday as doubt surrounds the Indian skipper’s availability at the SCG.

The 31-year-old emerged as a huge story on day two as cameras caught the paceman heading underneath the SCG to be whisked away for scans on a then unknown ailment.

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Bumrah, who has dominated the five-Test series against Australia with 32 wickets at an incredible average of 13.06, has experienced some niggles during the summer but has always taken his place in the side.

Yet the sight of Bumrah leaving the ground sent shockwaves through the sport as the world’s top-ranked bowler will be crucial to India’s hopes of bowling Australia out in its second innings and retaining the Border-Gavaskar Trophy.

Bumrah (right) walks through the bowels of the SCG to a waiting car. Picture: Sam Ruttyn

Bumrah managed a smile as he headed for scans. Picture: Sam Ruttyn

Over the past two Tests, Bumrah has also engaged in a running battle with teenage opener Sam Konstas, who will be key to Australia’s hopes on Sunday.

In Bumrah’s absence, the visiting attack did well to bowl Australia out for 181 in its first dig, a deficit of four runs, and fellow quick Prasidh Krishna was asked about Bumrah in Sunday’s post-match press conference.

“Yes he had a back spasm and went for scans and the medical team is monitoring him,” he said.

“So we’ll know whenever the medical team gets back to us.”

On a crazy day of Test cricket, India reached the close of play at 6/141, an overall lead of 145 runs.

The match is unlikely to make it into a fourth day, with both teams in the hunt to win the series.

Bumrah has dominated Australia throughout the series. (Photo by Saeed KHAN / AFP)

Bumrah’s battle with Sam Konstas has emerged as a key storyline. (Photo by Cameron Spencer/Getty Images)

If he is fit, Bumrah will firstly need to bat at the end of India’s second innings and then play his part with the ball.

Earlier on Saturday, Bumrah had been off the field for 42 minutes when he was seen leaving the SCG dressing room in his training gear along with team officials.

Virat Kohli acted as stand-in captain in the absence of Bumrah and Rohit Sharma, who “opted to rest” from the fifth Test.

Indian great Ravi Shastri said on Fox Cricket: “This could have a massive bearing on the series if it’s something serious.

“You just got the feeling he wasn’t OK. When he had that animated chat with Virat Kohli … you knew it was more than just to change his boots. Something must have happened.”

Brett Lee added: “It’s horrible news. You don’t ever want to see your strike weapon get whisked away in a car going to get scans.

“That’s a massive moment in this series.”

Bumrah returned to the SCG a couple of hours later, jogging up the stairs of the Members Pavilion.

At the end of day two, Adam Gilchrist and Kerry O’Keeffe discussed the situation as the news of Bumrah’s back issue filtered through.

“Just being told that in the press conference, a back spasm is how they’re describing it. Let’s hope that is the case,” Gilchrist said.

“That would warrant getting scans and making sure there’s no structural damage that’s going to create any issue further down the track.

Bumrah returning to the SCG after the scans. Photo: Fox Sports

“Hopefully for cricket lovers he’s out there with ball in hand at some stage in the second innings.”

O’Keeffe said the task ahead for both teams would change dramatically if India’s key threat is unable to bowl.

“Well there’s a target (for Australia) with Bumrah and without Bumrah,” he said.

“And without Bumrah is a much easier target.

“Otherwise, one of the three, if Bumrah’s there, (Mohammed) Siraj or Krishna, have to get five-for for India on the third day to win the game for India.”

The fifth Test will resume at the SCG at 10.30am AEDT on Sunday.

Originally published as Indian captain Jasprit Bumrah in fitness race against Australia