Djokovic made a promising start as he broke Navone’s serve at the first attempt, only to see a 4-1 advantage wiped out as he began to struggle in the humid conditions.

The catalyst for Djokovic’s troubles appeared to be a lengthy rally which sapped him of energy and left him struggling to recover.

A flustered Djokovic seemed to drop speed in both his serve and groundstrokes, calling out the doctor after the ninth game for some tablets to help alleviate what was bothering him.

He continued to look distressed as the opener moved into the tie-break – wearily bowing his head and bending over double between points – as Navone maintained his focus to strike first after one hour and 13 minutes.

As Djokovic toiled, an eerie hush fell around Arthur Ashe Stadium which indicated the crowd’s growing concern for the four-time champion.

The physical problems did continue to linger, but Djokovic perked up enough – seemingly helped by the cooler conditions under the roof – to level the match.

Djokovic becoming more animated in the early part of third set was a surefire sign he was starting to feel more like his old self, as was how he pounced on a poor service game from Navone to break for 5-4 and move ahead.

These are the positions from which prime Djokovic would usually go on to win, even when he was struggling physically.

The fact he was unable to do that against Navone, who has never gone past the second round in New York, was another indication of his declining powers.

What had been a tight match quickly ran away from Djokovic and became a difficult watch for the thousands still inside Ashe as local time fast approached midnight.

The atmosphere became subdued again as it became clear that Djokovic was not going to be able to wriggle out of trouble on this occasion.