The six-time Australian Open winner, and former world number one, was let down by his body and betrayed by his own game which Hyeon Chung picked up and played better than Djokovic himself. It was like Djokovic was a playing a fitter, faster version of himself.

For the first time since 2007 Djokovic failed to win a set in a match at the Australian Open and on that occasion he was 20 and playing Roger Federer. Indeed, it has been more than a decade since Djokovic has failed to win a set at a hardcourt grand slam.

Djokovic was beaten by the bespectacled 21-year old South Korean, who himself dolefully admits still no one knows him at home.

"Tennis, not that popular in Korea," he said after beating the world number three Alexander Zverev in the last round. After beating Djokovic he is likely to be a little more familiar in Seoul next time. And who knows how far he can go yet, for he confronts American Tennys Sandgren next and he too is in virgin territory in a slam quarter-final.

It did however feel like Djokovic was complicit in his own demise, partly because his body let him down, partly because he got a taste of what it is like to play himself. Chung was incredibly quick across the court, running everything down and and yet had the freedom and touch in his ground strokes to hook crosscourt forehands on the run from deep in the court. He had four times backhand winners to Djokovic's.

Djokovic's right elbow was seemingly held together with an elastic sleeve. The elbow had kept him out of the game for six months last year and it now appears he might need more time to rest or consider other medical options. He grimaced his way through the match, had treatment from physios at length and then seemed to pull up short from his hips or groins that had also troubled him in the previous round.

'Look, you know, I haven't played six months. We have to take that in consideration. I've played a long match against Gael [Monfils] a few days ago. I mean, this didn't happen too many times in my career that I have maybe some tensions in the muscles or whatever, some kind of physical challenges," Djokovic said after the last round.

The pain he was clearly in during the match suggests this was not a fitness issue but an injury issue. He did not look short of a step, he looked short of a shot.

Djokovic pushed routine volleys long or wide, he double-faulted almost as routinely as he normally hits those volleys he was missing. Djokovic served four straight double faults a cross his first two service games. He finished with nine for the match.

This doesn't look like the rejuvenation of Roger after a lay-off, this looks like an enforced break that should have been longer and this looked more like a generational battle. Djokovic is not old but he was made to look it by his body and the agility of Chung.