Stefanos Tsitsipas maintained his unbeaten record in grand slam quarter-finals with victory over Jiri Lehecka to reach the last four at the Australian Open.The third seed made it six from six in the last eight at majors with a 6-3 7-6 (2) 6-4 victory over 21-year-old Lehecka, who had never won a grand slam match before arriving in Australia.The young Czech had defeated Cameron Norrie and Felix Auger-Aliassime to make the last eight but was broken in his first service game and, although he put on a creditable display, it was not enough to take a set from Tsitsipas.The Greek, who along with Novak Djokovic still has a chance of finishing the tournament as the world number one, will take on Karen Khachanov in the semi-finals on Friday.Earlier, Khachanov reached a second consecutive slam semi-final after Sebastian Korda retired with a wrist injury when trailing 7-6 (5) 6-3 3-0.The 22-year-old American has been one of the stories of the tournament, defeating Daniil Medvedev and Hubert Hurkacz to reach a first slam quarter-final 25 years after his father Petr lifted the trophy.But he took a medical time-out after five games of the second set to have his wrist taped and called it quits after losing the next seven games.Korda said of the injury: “I had it a little bit in Adelaide a couple weeks ago but then it went away.
During the matches, it was completely fine. Then, just one kind of mis-hit return and it started to bother me a lot after that.“Some forehands, I couldn’t even hold the racket.
Volleying was almost impossible for me. So it was a little tough.”It has nevertheless been a breakthrough fortnight for Korda, and he added: “There is a lot of positives, way more positives than negatives.Read more on independent.co.uk