From the moment Djokovic lunged for a drop-shot towards the end of the first set against Alcaraz and immediately grimaced to his box, there have been questions over his fitness.

Djokovic, as he has on countless occasions in his stellar career, somehow managed to defy the injury to earn a remarkable win against the 21-year-old.

But doubts remained how equipped he would be to play Zverev.

“I knew even if I won the first set, that it’s going to be a huge uphill battle for me to stay physically fit enough to stay with him,” added Djokovic.

“I don’t think I had that in the tank.”

Djokovic had not practised at Melbourne Park since Tuesday night’s victory, cancelling a planned hit on Thursday before spending an hour warming up on court shortly before the semi-final.

Djokovic did not practise between matches during his 2023 title run and later revealed he had a three centimetre tear in his hamstring.

He also won the 2021 title despite tearing an abdominal muscle in the third round.

“The very first thing I want to say is, please guys, don’t boo when a player is injured,” said Zverev, addressing the crowd in his on-court interview.

“I know everyone paid for tickets and wants to see a five-set match but you have to understand Novak Djokovic is someone who has given absolutely everything to tennis.

“He has won this title with an abdominal tear, he has won this title with a hamstring tear.

“If he cannot continue this match, it means he really cannot continue.”

Former Australian player John Millman, working at Melbourne Park as a television summariser, said the crowd’s reaction showed a “total lack of respect”.

He added in a post on X: “Novak getting booed off is a disgrace. Classless.”