Novak Djokovic through to last 16 as Mikhail Youzhny forced to retire

The Russian was struggling almost from the start, requiring a pause for treatment early on.

But after barely 20 minutes he gave up, handing Djokovic the win with the score standing at 4-2.

"It's difficult to pick the words now. I don't think I ever had this kind of situation in my career, where I had a second-round walkover and the third round 30 minutes only," Djokovic said on court before heading off to practice.

"I'll try to get the positives out of these six games. Obviously I did start very well with a good intensity and I'll try to carry that into the next match."

That next match will be against either Britain's Kyle Edmund or America's John Isner.

It is the second match in a row that Djokovic has benefited from a withdrawal: in his second round match he didn't even have to step onto the court as Jiri Vesely failed to recover in time.

While some might lament the lack of match practice, Djokovic will be hugely relieved: he has been struggling with injuries and form of late, not to mention serious off-court problems which by his own admission affected his focus.

He came through a four-setter in his opening round match against Jerzy Janowicz, but Djokovic will enter the second week having played just four and a half sets of tennis, and a total of just 42 games.

And while staying fresh is one thing, results elsewhere in the draw - and specifically the defeat of Marin Cilic on Friday - mean that Djokovic cannot now face a world top 10 player until he lines up in the semi-finals. Assuming, of course, that he does make it that far.