World’s No. 1 Novak Djokovic of Serbia advanced to the semifinals of the 2019 Australian Open after his quarterfinals opponent Kei Nishikori of Japan retired in the second set trailing behind the Serb 1-6; 1-4.

Axar.az reports citing Russian media.

The No. 8 seed Nishikori asked for a medical assistance after the opening set of his match against Djokovic at the Rod Laver Arena and received a strapping to his right thigh. However, he called it quits in the 2nd set, just 52 minutes into the match.

According to the statistics of provided by the tournament’s official website, the 29-year-old Japanese player had spent a total of 13 hours and 47 minutes to reach the quarterfinals since the opening match of the 2019 Australian Open, which has $44.5 million in prize money up for grabs and runs between January 14 and 27.

Nishikori’s path to the quarterfinals included three five-set contests and two fightbacks from two sets down as well as almost five-hour long clash with Spain’s Pablo Carreno Busta in the 4th round, which saw Nishikori snatching the victory of 6-7 (8-10); 4-6; 7-6 (7-4); 6-4; 7-6 (10-8).

"I love to battle, especially against Kei," Djokovic was quoted as saying after the match. "We’ve played so many matches throughout our careers, especially here a couple of times years ago. I hope he can recover, and it’s not something very serious."

Djokovic, who is currently on his quest to win the 7th record champion’s title of the Australian Open, is set to meet in the semifinals 28-seed Lucas Pouille of France. The 24-year-old French player is playing at the Australian Open tournaments since 2014, but he never managed to clear the first stage.

"I’m looking forward for a battle, obviously," Djokovic said speaking about his upcoming clash with Pouille. "It’s his first semifinal at a Slam, but he has won against [Rafael] Nadal in New York some years ago, and he has taken a couple of scalps at the big tournaments, so he’s not afraid to play his best on the biggest stages in our sport."

"I expect him to come out and be very confident in himself as he always is, and I’m looking forward to it," Djokovich added.

In the other semifinal match on January 24 in Melbourne, Spanish tennis star Rafael Nadal (seed-2) will take on 20-year-old Stefanos Tsitsipas of Greece (seed-14). Nadal won his sole Australian Open title ten years ago and the upcoming semifinal in Australia will be the 6th one in his career. The Spanish player holds the champion’s titles of 17 Grand Slam tournaments in men’s singles, which ranks him the second best in the history of tennis.