The 37-year-old Briton has been working with his long-time playing rival on a trial basis in Melbourne.

Murray, who retired in August last year, took a surprise coaching role with Djokovic’s team in late November.

After overcoming injury to beat Spanish third seed Carlos Alcaraz in the quarter-finals, Djokovic was forced to retire from his semi-final against German second seed Alexander Zverev on Friday.

“Novak and I agreed that after the tournament we would speak – and we will do that,” Murray said afterwards.

Djokovic said the pair would need to “cool off” before discussing the future.

“We are still hot-headed and disappointed, so it’s kind of hard to switch the page and start talking about what the next steps are,” said the 37-year-old Serb.

“We are both disappointed with what just happened, so we didn’t talk about the future.

“I’ll definitely have a chat with Andy and thank him for being here with me.

“I’ll give him my feedback, which is positive, and see how he feels and we will make the next step.”

It is no secret that Djokovic is a challenging guy when it comes to his pursuit of greatness.

After winning a men’s record 23rd Grand Slam title at the 2023 French Open, Djokovic admitted he had been “torturing” his team during the tournament.

“He’s not an easy guy, let’s put it this way – especially when something’s not going his way,” said then-coach Goran Ivanisevic, who joked Djokovic “chained” his team “with handcuffs”.

Murray said before the Australian Open started that the work had already been “demanding” – despite having only linked up for a 10-day practice block in Spain and a few days in Melbourne.

He also knew it would become more “stressful” during the tournament.

After Djokovic’s run ended in unfortunate circumstances, Murray said the experience had been “a steep learning curve”.

“I’ve certainly learned a lot but there’s a lot more still for me to learn, that’s for sure,” the Scot added.

Whether it is providing detailed insight about an opponent or carrying his racquets to the stringer, Murray has had Djokovic’s back in Melbourne.

The former world number one was even chasing down drop-shots at the end of practice sessions.

Over the past fortnight, Murray showed he was willing to do whatever it takes to help Djokovic win a record 25th Grand Slam title.

“They’re in this together,” Murray’s former coach Dani Vallverdu told BBC Sport.

“It’s the feeling of the older guys against the younger guys – that’s what’s driving them.”

Born a week apart in May 1987, Murray and Djokovic first became acquainted as 12-year-olds at junior tournaments.

The rivalry continued into the senior game as they met in 36 tour-level matches, including seven Grand Slam finals.

“Having someone in his box, and the locker room, who has been through it all on the opposite side of the court gives Novak a feeling of familiarity,” said Vallverdu, who was part of Murray’s team when he beat Djokovic to win Wimbledon in 2013.

“There is someone who understands him and has understood him from the other side of the court.”

Murray also knows Djokovic’s potential opponents inside out.

Murray had played everyone Djokovic faced from the third round onwards in Melbourne – Tomas Machac, Jiri Lehecka, Alcaraz and Zverev – in the past four years.

“I know what the speed of their serve is like, what the top-spin on their shots is like, and hopefully have a decent understanding of their strengths and weaknesses,” Murray said.

During Djokovic’s victory over Alcaraz, former British number one Annabel Croft spotted the Serb going low down the middle during the rallies.

Asked afterwards by a small group of British reporters about his tactical input, Murray grinned.

He refused to take the credit, insisting it was all Djokovic’s own work.

But given his meticulous attention to detail, it would be a surprise if Murray isn’t studying hours of video footage and combing through statistics.

“When Andy played he was one of the more data-driven players out there,” said former Australian player John Millman, who is working as an analyst, external with host television broadcaster Channel Nine.

“He felt better going into a match with that wealth of information. I’m sure he’s brought that into the Djokovic camp.”

At Melbourne Park, there were plenty of chances to see how the team dynamic works.

Murray often worn a serious expression during Djokovic’s matches. Motivating fist pumps were rare, tactical exchanges sparse.

While Djokovic often looked over to his team, there were fewer outbursts than we have been used to seeing.

After his victory over Alcaraz, Djokovic walked straight over to Murray and buried his head in his chest.

“It was kind of a gesture of appreciation and respect for him for the fact that he’s out there and he doesn’t need to be,” said Djokovic afterwards.

During practices, Murray watched every movement intently from close quarters.

Afterwards they usually shared a warm hug and sometimes had a gentle knock.

Then it was back to collecting Djokovic’s racquets and taking them to the stringer.

“When I saw Andy walking through the corridors with all Novak’s racquets, taking them to the stringer, you could see he is taking this job very seriously,” Australian former world number four Sam Stosur told Channel Nine.

Djokovic’s pre-tournament practice sessions against Alcaraz, Jack Draper and Arthur Fils offered more insight.

Standing close behind Djokovic and sometimes in the doubles alley, Murray constantly offered feedback, shouted praise after winners and made notes.

He also compared observations with Boris Bosnjakovic, who ran Djokovic’s training centre in Belgrade before becoming part of the team last May after long-term coach Ivanisevic left.

“The team has done an incredible job over many, many years to allow him to still be competing at this level at the age that he’s at,” said Murray.

“They’ve all been really, really helpful to me. They really welcomed me. It’s been great to be a part of.”

Djokovic, who was bidding for a record-extending 11th title, quit after losing the first set 7-6 (7-5) in 80 minutes.

The 37-year-old Serb had his upper left leg heavily taped after injuring it in Tuesday’s quarter-final win over Carlos Alcaraz.

“I did everything I possibly could do to manage the muscle tear that I had,” said Djokovic, who was also aiming for an all-time standalone record of 25 major titles.

“Towards the end of that first set I just started feeling more and more pain.

“It was too much to handle for me.”

After he slapped a volley into the net on set point, seventh seed Djokovic immediately approached Zverev and shook his hand.

He waved to the crowd and gave them a double thumbs up, despite audible boos from some sections inside Rod Laver Arena.

Asked by Serbian media, external about the reaction, Djokovic said: “I don’t know what to say.

“People have come and paid for the tickets expecting a great match and a big fight, which they didn’t get.

“From that perspective, I can understand. I am doing my best to understand them, but I am not sure whether they understand me or if they even want to.”

German second seed Zverev is still bidding for his first Grand Slam title after twice losing in major finals.

He will face world number one and defending champion Jannik Sinner in Sunday’s final after the Italian beat Ben Shelton.

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.”

Djokovic looked way below his best from the start of the semi-final.

The former world number one was fortunate not to be punished more by Zverev as he struggled badly with his first serve.

Zverev, playing passively behind the baseline, produced poor errors on the four break points he created in the third game of the match.

Two forehands and a backhand were meekly dumped into the net before he framed a forehand into the front rows of the stand on the fourth.

After three slogs of games spanning 23 minutes, Djokovic had three break points himself at 2-1 but could not take his chances.

Djokovic’s service games improved but he had to save another break point at 4-4, and the laboured walks to the chair and anguished facial expressions became more pronounced.

Nevertheless, ending the match early came as a shock to most of the 15,000 crowd on Rod Laver Arena – and Zverev himself.

Asked if he had any indication Djokovic was struggling, Zverev laughed: “No, I actually thought it was a high-level set.

“Of course there were some difficulties and the longer you continue maybe the worse it gets.

“Maybe in the tie-break he was not moving as well, but I thought we had extremely long, physical rallies.”

The 37-year-old Serb defied injury, age and ranking to win 4-6 6-4 6-3 6-4 against his 21-year-old opponent in Melbourne.

“It was possibly one of the best matches of the tournament on the men’s side,” said Djokovic.

“It felt like a final of a Slam and I wish it was. We both gave it our all.”

Djokovic, going for a record-extending 11th men’s singles title, limped around Rod Laver Arena at the end of the first set with a problem in his upper left leg.

But, after going off court for treatment, he recovered impressively to continue his bid for a 25th Grand Slam triumph – which would be an all-time record.

Djokovic played aggressively until the pain wore off, which then allowed him to move more freely and take control.

Spanish third seed Alcaraz became increasingly animated as he struggled to figure out how to turn an engrossing contest back in his favour.

When seventh seed Djokovic sealed victory – at 00:57 local time after a battle lasting three hours and 38 minutes – he roared towards coach Andy Murray.

Djokovic and Alcaraz shared a warm embrace at the net after a highly-anticipated match which lived up to the expectation.

“When Novak plays at this level, it’s really difficult. It was a really close match,” said Alcaraz.

The defeat ends Alcaraz’s hopes – for now, at least – of becoming the youngest man to complete the career Grand Slam.

Instead it is Djokovic who advances to the semi-finals, where he will face German second seed Alexander Zverev on Friday.

For so many years, Djokovic has defied the ageing process with his endurance and dexterity.

This was the latest example – at a time when few had predicted it.

Time, it seemed, had eventually started to catch up with a player who is aiming to become the oldest Grand Slam men’s singles champion in history.

Last year was the first since 2017 – and only the second since 2010 – that he did not win one of the sport’s four major prizes.

Doubts had already been raised about his ability to outlast the very best of his younger opponents – namely Alcaraz and world number one Jannik Sinner – over five sets.

His aura of invincibility at Melbourne Park was damaged last year when Sinner dominated their semi-final to end his 33-match winning streak at the venue.

Then Alcaraz walloped him in the Wimbledon final – albeit in a match that came less than six weeks after Djokovic had surgery on a tear in his knee.

However, Djokovic won his last encounter with Alcaraz, putting in a ferocious display at the Olympics to claim a gold medal which had previously eluded him.

A more patient approach in the first set on Tuesday was quickly replaced after he tweaked something lunging for a drop-shot.

Employing more aggression was a risk-reward strategy but necessary given his physical condition. It paid off.

Djokovic cracked 11 winners, including a rasping backhand on set point to level the match, as he successfully negotiated his way through a barrage of Alcaraz drop-shots.

Alcaraz’s service games at the start of the third set continued to come under heavy fire. He buckled when Djokovic broke for 4-2, with the third seed losing serve again for 5-3 after he had seemingly rescued the situation.

Djokovic used the momentum to break in the first game of the fourth set – which ultimately proved decisive.

After surviving three break points and recovering from a host of long, energy-sapping points, Djokovic held his nerve to serve out a memorable win.

On being ready to play again on Friday, he said: “I’m concerned physically but if I can somehow manage to be physically ready, I’m mentally and emotionally as ready as I can be.”

While many thought Djokovic was the underdog going into Tuesday’s match, Alcaraz knew the size of the task he faced.

The four-time major champion pointed to Djokovic’s greater experience and his “unbelievable” fitness, but insisted he would not be daunted by facing the man widely regarded as the greatest player of all time.

After a nervy start, he warmed to his task.

The intensity of Alcaraz’s game, returning from seemingly-impossible positions with venomous power, seemed to take a toll on Djokovic.

But the younger player became befuddled as Djokovic’s aggressive tactics, which particularly targeted Alcaraz’s backhand, paid dividends.

“I felt like I was controlling the match and I let him get into it again,” said Alcaraz, who has not gone past the quarter-finals in four Melbourne appearances.

“I’m going to say that was the biggest mistake that I made.

“In the second set I had to play a little bit better just to push him even more to the limit.”

The 37-year-old was made to work in his 430th Grand Slam singles match but he emerged triumphant, beating qualifier Jaime Faria 6-1 6-7 (4-7) 6-3 6-2.

The win gives Djokovic sole ownership of the all-time record for most Grand Slam singles matches played among men and women, and takes him past former rival Federer, who played his last major match at Wimbledon in 2021.

“I love this sport. I love competition,” Djokovic said when asked about the milestone.

“I try to give my best every single time. It’s been over 20 years that I’ve been competing in Grand Slams at the highest level.

“Whether I win or lose, I will always leave my heart out on the court. I’m just blessed to be making another record.”

The victory also meant the Serb became the first man over the age of 30 to reach 150 Grand Slam singles wins.

Djokovic can make further history still in Melbourne – win the title and he would claim a 25th major, moving him clear of Australia’s Margaret Court as the sole leader of all-time Grand Slam singles titles.

The seventh seed, who has three-time Grand Slam champion Andy Murray in his coaching box, will face Czech 26th seed Tomas Machac in the third round.

Norwegian sixth seed Casper Ruud became the biggest casualty in the men’s draw, losing 6-2 3-6 6-1 6-4 to 19-year-old Czech Jakub Mensik.

World number 48 Mensik and Joao Fonseca, the 18-year-old Brazilian qualifier who stunned ninth seed Andrey Rublev on Tuesday, are the first teenagers to beat top-10 opponents at the same Grand Slam since Djokovic and Murray at Wimbledon in 2006.

Meanwhile, German second seed Alexander Zverev claimed an assured 6-1 6-4 6-1 victory over Spain’s Pedro Martinez to set up a third-round meeting with Britain’s Jacob Fearnley.