Australian Open updates: Novak Djokovic to face Lucas Pouille in semi-finals, Karolina Pliskova sets up clash with Naomi Osaka

World No 1 Novak Djokovic reached the Australian Open semi-finals in a hurry as an ailing Kei Nishikori retired when losing 6-1, 4-1 after just 51 minutes. Nishikori had endured three five-set epics during 13 hours and 47 minutes on court before the quarter-final clash, and suffered a thigh strain in the first set as the marathon matches took their toll. Eighth seed Nishikori began to suffer early in the first set and was a shadow of his usual fighting self as he lost it in 31 minutes. After a medical timeout and three minutes of treatment from the physiotherapist, Nishikori emerged for the second set with his right thigh strapped and courageously attempted to carry on. He seemed to be moving a little more freely, but the recovery did not last long. After being broken to go 2-1 down by the Serbian 14-time Grand Slam champion Nishikori became almost immobilised. When Djokovic broke again to go 4-1 ahead it proved the last straw for Nishikori's brave challenge. "I love to battle, especially against Kei, we have played so many matches in our careers," said the Serb, who is chasing a record seventh Australian Open title. "I hope you can recover. I hope it's not something serious that will take too long. I wish him a speedy recovery. I'm sorry for everybody for not having a full match tonight but thank you for showing up." Lucas Pouille became the first Frenchman to reach the semi-finals of the Australian Open since Jo-Wilfried Tsonga in 2010 when he stunned Canada's 16th seed Milos Raonic . Pouille, the 28th seed, fought back from a break down in the first set to win 7-6, 6-3, 6-7, 6-4 and reach the last four of a slam for the first time. The 24-year-old had never won a match at Melbourne Park before this year but on Friday will face either Novak Djokovic or Kei Nishikori for a place in the final. Pouille recently recruited 2006 Australian Open champion Amelie Mauresmo to his team after a splitting with long-time coach Emmanuel Planque in the off-season. But the world No 31 arrived in Melbourne in poor form: he had lost all three of his singles matches at the Hopman Cup and suffered a first-round exit at the Sydney International. "I'm very happy," Pouille said. "I was trying to forget the start of the year. "I just kept working hard. All the matches I decided to take step by step, give everything on every point and here I am. "Last year I lost a bit of joy being on the court. I started a new adventure with my team, with Amelie. I enjoy being on the court again and that is the most important." Serena Williams's bid to equal Margaret Court's record 24 grand slam titles was brought to a halt in sensational style by Karolina Pliskova, who will face Naomi Osaka in the Australian Open semi-finals. The American had beaten world No 1 Simona Halep in the fourth round but folded against the big-serving Czech seventh seed, who saved four match points before winning 6-4, 4-6, 7-5 under the hot Melbourne sun. It was a gut-wrenching defeat for the 37-year-old, who battled back from a set down and was leading 5-1 in the third and serving for the match, only to throw it away with some poor serving and wild shots as frustrations bubbled to the surface. "She was playing very well. Especially at the end of the second set she went for her shots and she was aggressive," said Pliskova after depriving Williams of a US Open final rematch with Osaka. "I played too passive. I was almost in the locker-room but now I am standing here as a winner. It is a very good feeling." _____________ Read more: _____________ Japanese fourth seed Naomi Osaka routed an injured Elina Svitolina to reach the Australian Open semi-finals on Wednesday. The US Open champion beat the Ukrainian sixth seed 6-4, 6-1 to set up a final four clash with Czech seventh seed Karolina Pliskova. It was the 21-year-old's second straight grand slam semi-final after her triumph at Flushing Meadows, and she is the first Japanese woman in the final four at Melbourne Park since Kimoko Date in 1994. Svitolina received treatment for a neck or shoulder injury in the second set and looked a shadow of the player that won the WTA Finals in Singapore last October. "I tried to be consistent, it's unfortunate that she got injured but playing against her even when she was injured was still really tough," Osaka said. She was pleased to maintain her composure in a simple straight sets win after previously losing her cool on court when her last two matches went to three sets. "I just had one goal, to try as hard I can and not get angry," she said. "I didn't do that really well in the last two rounds and I did that today, so I'm really happy with the way I played." ____________ Read more: Comment: Get used to more awkward speeches - Naomi Osaka is here to stay ____________

Australian Open updates: Novak Djokovic to face Lucas Pouille in semi-finals, Karolina Pliskova sets up clash with Naomi Osaka

A round-up from Wednesday's quarter-final matches at Melbourne Park