Osaka moves past Muchova to reach US Open semi-finals

Naomi Osaka returned to the US Open semi-finals on Wednesday with a 6-4 7-6(3) win over Karolina Muchova, as the four-times Grand Slam champion delivered a battling display to underline her resurgence on the sport's biggest stage.

Four years after winning the last of her four major titles, the Japanese 23rd seed, who returned last season after a lengthy maternity break, stretched her unbeaten run in major quarter-finals to 5-0 and booked a clash with Amanda Anisimova.

Muchova, who had been on court for more than 10 hours over four draining rounds, took treatment in the locker room for an apparent left leg issue after she dropped a tight opening set, but came out firing to break at the start of the next.

She struggled to move at times with heavy strapping on her thigh but continued to frustrate her opponent with her inventive brand of tennis to break for a 5-4 lead, only for Osaka to wrest back the initiative and go through after the tiebreak.