Novak Djokovic has reached the semi-finals of the Australian Open after Kei Nishikori retired hurt when trailing 6-1 4-1 in their quarter-final.
Nishikori had a medical time-out between sets, with the trainer working on a right thigh problem.
Top seed Djokovic will meet Lucas Pouille for a place in the final.
Pouille reached his first grand slam semi-final at the Australian Open with a four-set upset of Milos Raonic.
Pouille, the 28th seed, had lost in the first round on his five previous visits to Melbourne but his 7-6(4) 6-3 6-7(2) 6-4 victory over big-serving Canadian Raonic was the latest in a series of strong performances this fortnight.
He recovered from a break down to win the opening set, his first in four meetings with Raonic, and put the loss of the third set aside to come through strongly.
Pouille reached the quarter-finals of Wimbledon and the US Open in 2016 but struggled to build on that and endured a disappointing 2018.
There was little to indicate he was about to go on such a run after beginning this season with four defeats but he gave credit to coach Amelie Mauresmo, who he hired in the off-season.
Pouille is following in Andy Murray's footsteps as a top male player to hire a a female coach - in this case the same one - and, replying to John McEnroe's assertion in the on-court interview that more men should look to women as coaches, the 24-year-old said: "They should."
