Novak Djokovic into 2019 Australian Open Semi-Finals After Kei Nishikori Retires

Novak Djokovic advanced to the semi-finals of the 2019 Australian Open after an exhausted Kei Nishikori retired from their last-eight clash on Wednesday. 

The Japanese star, who played three five-setters in his first four rounds in Melbourne, including a five-hour marathon against Pablo Carreno Busta on Monday, called time on the match at 6-1, 4-1 behind.

Djokovic had dominated for 52 minutes, and the eighth seed visibly struggled from the opening game, receiving treatment between the first and second sets.  

The world No. 1 will now face Frenchman Lucas Pouille for a spot in the final. 

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Nishikori, 29, is at his best when he can show off his incredible movement and immense stamina.

When on top form he can compete with even the best players going down the stretch, but it was obvious from the start on Wednesday that he was a spent man.

Nishikori was broken to go 2-0 down in his opening service game of the match.  

Rather than attempting to go toe-to-toe with Djokovic from the baseline he approached the net a lot more than usual.

But that plan did not work as he was easily passed by the Serbian to go a double break and 5-1 behind in the opener.

The top seed sealed the set in 31 minutes and there looked to be no way back even then for Nishikori:

He was forced to go for every line in an attempt to shorten the rallies but invariably missed by a long way, making 19 unforced errors in the opening set.

It was more of the same in the second set, even after he received treatment on his right thigh, and it was tough to watch:

Rather than prolong the misery after he was broken for a second time in the second set, Nishikori approached Djokovic and conceded the match.

It is likely not the way Djokovic would have wanted the match to end. But it does mean he will be fresh for the clash against Pouille as he continues his campaign to win a record seventh Australian Open title.