With an injury-ravaged side and under a stand-in skipper, India overcame the odds to retain the Border-Gavaskar Trophy with a stirring Gabba win on Tuesday.

India were bundled out for a record low of 36 in Adelaide and regular skipper Virat Kohli left a demoralised team behind to returned home for the birth of his daughter.

Under Ajinkya Rahane, India levelled the series in Melbourne and drew in Sydney. They had lost their entire frontline bowling attack to injuries by the time they arrived in Brisbane.

Net bowlers Washington Sundar and T Natarajan were then called upon to make their test debut, helping India pull off a series victory for the ages, prevailing by three wickets in the decider.

"I'm not someone who really has tears in my eyes but I had real tears because this is unreal," Shastri told a video conference.

"The penny has still not dropped, and it will take a long time to drop. Unreal."

Playing his first series, opener Shubman Gill laid the foundation for India's chase with a classy 91 and number three batsman Cheteshwar Pujara took several blows on his body and helmet during his stubborn 56.

Rishabh Pant then smashed an unbeaten 89 in a match-winning chase to complete a heroic series win for the tourists.

"What these guys have pulled off will go down in history as one of the greatest series ever played," Shastri said.

"When you take the COVID situation and the spate of injuries into account, showing stomach for a fight after being bowled out for 36 is unimaginable."

The challenges of living in a bio-secure bubble and the spate of injuries made it the toughest tour he could remember, the former test player said.

"This is the toughest tour ever. We're playing in COVID times, quarantine times and with the multiple injuries - nothing comes close. It surpasses all."

Rahane inspired India's comeback with a captain's century in Melbourne, and he was his modest best after the win.

"I was emotional too. I still don't know what happened and don't know how to describe this," said Rahane, who gifted a signed India jersey to Australia's Nathan Lyon on the spinner's 100th test after the match.

Australian Associated Press