India's most potent bowler sent down just one over in the second session before leaving the field, and later exited the SCG in his training kit.
The quick was then spotted entering a car and being driven out of the carpark behind an ambulance, presumably to undergo scans.
Is this the series deciding moment? Jasprit Bumrah receives an ambulance escort out of the Sydney Cricket Ground after leaving the field with injury. @9NewsAUS @wwos pic.twitter.com/88fcTNDKsQ— Sam Djodan (@samdjodan) January 4, 2025
Any absence of Bumrah would raise significant questions over their ability to win in Sydney and retain the Border-Gavaskar Trophy by drawing the series at 2-2.
While India bowled Australia out for 181 at tea on Saturday to claim a four-run lead, they will desperately want their strike bowler available for the last innings.
Bumrah's speed was well down in the over he did bowl on Saturday afternoon, but there was no visible sign of a limp as he left the ground.
Regardless, the 31-year-old could well have just bowled himself into the ground this series while carrying India on his back.
The 53.2 overs he bowled in the Boxing Day Test were the most he has sent down in any match of his career, with that fixture only finishing on Monday.
At one point on day four in Melbourne, Rohit asked Bumrah to bowl another, to which the quick replied: "Enough now, I'm not able to push more."
Bumrah has sent down 151 overs for the series, the most of any Indian player.
At times his bowling has kept his side in Border-Gavaskar Trophy, with Bumrah's 32 wickets at an average of 13.06 the most of any Indian quick in one series.
The right-armer has already had to overcome injury concerns during the series, with treatment needed on his groin during his side's 10-wicket loss in Adelaide.
There had been concerns he would not be fit to play in the third Test in Brisbane, but the prodigious seamer was able to train freely in the lead up to that match.
India's reliance on Bumrah has also been increased by the fact they have been without Mohammed Shami for the entire series, owing to long-running knee and ankle injuries.
Bumrah's exit on Saturday left former Test captain Virat Kohli to marshal the Indian side during Australia's first innings, with full-time skipper Rohit Sharma out of the team.
Bumrah had taken 2-33 from his 10 overs before his injury, dismissing Usman Khawaja (2) on the last ball of day one before snaring No. 3 Marnus Labuschagne (2) cheaply as well.