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.”