BBC Sport tennis news reporterPublished18 minutes agoNovak Djokovic broke down in tears during a US Open first-round defeat by Argentina's Mariano Navone which provided further evidence age is fast catching up with the 39-year-old great.
The 24-time Grand Slam champion was overcome by emotion in the deciding set of a dramatic match where he struggled physically throughout and had to vomit into a towel bin.
Djokovic, seeded fourth in New York, showed the fight for which he has always been renowned before succumbing to a 7-6 (7-5) 5-7 4-6 6-2 6-1 loss.
It was the first time the Serb had been beaten in the opening round at Flushing Meadows and the first time he had lost in the opening round of a Grand Slam tournament since 2006.
Djokovic managed to raise a smile as he congratulated 25-year-old Navone on what will rank as one of the biggest victories of the world number 49's career.
But, after showing grace and class while congratulating his opponent, a disconsolate Djokovic was unable to keep a brave face for long and appeared close to tears again as he trudged back to the locker room.
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The catalyst for the former world number one's troubles appeared to be a lengthy rally which sapped him of energy and left him struggling to recover.
A flustered-looking Djokovic seemed to drop speed in both his serve and groundstrokes as the first set continued, calling out the doctor after the ninth game for some tablets to help alleviate what was bothering him.
Djokovic 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.
So often Djokovic has found a way to win in moments of adversity. Was this going to be another example?
The physical problems did continue to linger, but Djokovic perked up enough - seemingly helped by the cooler conditions under the roof - to create the only break points of a finely-poised second set.
After missing chances in the third and fifth games, he dug deep to strike for a 6-5 lead and served out to love as he levelled 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 - although not for too long.
With the set locked on serve at 3-3, Djokovic looked unsteady on his feet again before pouncing on a poor service game from Navone to break for 5-4 and holding serve to move into the lead.
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 with local time fast approaching midnight.
The atmosphere became increasingly subdued again as it became obvious Djokovic was not going to be able to wriggle out of trouble on this occasion.
