The curious case of Ashwin's Test hopes

Less than three hours after Ravichandran Ashwin was ruled out of the fourth Domain Test, the veteran off-spinner was back in India's squad.

Ashwin is part of a 13-man squad that includes left-arm wrist-spinner Kuldeep Yadav, reserve batsman KL Rahul and express fast bowler Umesh Yadav.

Missing are injured quick Ishant Sharma (rib cage discomfort) and batsman Rohit Sharma, that latter of which returned home to Mumbai in the wake of India's 137-run win in the Boxing Day Test for the birth of his child.

An India spokesperson confirmed at midday today Ashwin was not 100 per cent fit and would not be considered for selection in Sydney.

However, Ashwin will now be given until the morning of the Test to prove his fitness.

The 32-year-old suffered a side strain in the first Test in Adelaide and has missed the past two matches in the series.

Upon hearing the news that Ashwin was ruled out, Australia skipper Tim Paine appeared relieved the former world No.1 bowler would not be taking the field in Sydney.

"That's good news," Paine said. "I saw him bowl yesterday and he was batting in Melbourne, so I'm surprised he's not playing.

"I think conditions here would have suited him really nicely. Normally it spins quite a bit and with his height he would've been a handful, so I think some of our batters will be pretty happy to hear that news.

"But we know they've got some other spinners in their squad, Kuldeep is younger but got some serious talent and Jadeja did the job for them in Melbourne."

Kuldeep, 24, played the last of his five Tests against Australia in Dharamsala in March 2017, where he took 4-68 in the visitor's first innings in the series-clinching eight-wicket win.

The presence of Rahul in the side suggests India are contemplating reinstating him to the top of the order and shuffling Vihari to No.6 to cover for Rohit.

The SCG Test looms as one of the most important in India's history, with a win, draw or tie securing the nation's maiden Test series win on Australian soil.

India squad: Virat Kohli (c), Ajinkya Rahane (vc), KL Rahul, Mayank Agarwal, Cheteshwar Pujara, Hanuma Vihari, Rishabh Pant, Ravi Jadeja, Kuldeep Yadav, Ravi Ashwin, Mohammed Shami, Jasprit Bumrah, Umesh Yadav

Domain Test Series v India

Dec 6-10: India won by 31 runs

Dec 14-18: Australia won by 146 runs

Dec 26-30: India won by 137 runs

Jan 3-7: Fourth Test, SCG

Australia squad: Tim Paine (c, wk), Josh Hazlewood (vc), Mitch Marsh (vc), Pat Cummins, Aaron Finch, Peter Handscomb, Marcus Harris, Travis Head, Usman Khawaja, Marnus Labuschagne, Nathan Lyon, Shaun Marsh, Peter Siddle, Mitchell Starc

India squad: Virat Kohli (c), Murali Vijay, KL Rahul, Mayank Agarwal, Cheteshwar Pujara, Ajinkya Rahane, Hardik Pandya, Hanuma Vihari, Rohit Sharma, Rishabh Pant (wk), Parthiv Patel (wk), Ravi Ashwin, Ravi Jadeja, Kuldeep Yadav, Mohammed Shami, Ishant Sharma, Umesh Yadav, Jasprit Bumrah, Bhuvneshwar Kumar