Croatian Marin Cilic is through to the semi-finals of the Australian Open after No.1 seed Rafael Nadal retired from their quarter-final on Rod Laver Arena.
Nadal received treatment for a leg issue in the fourth set before he succumbed down a break in the fifth set with Cilic leading 3-6 6-3 6-7 (7-5) 6-2 2-0.
"Sometimes in these occasions where a player gets hurt a bit you're not exactly sure what are his possibilities ... how is he going to come up," Cilic said.
"I just tried to stay in my own box and continue with playing well, continue with that intensity. I kept with my own game, with the plan, obviously it paid up.
"In the end I was very unfortunate because Rafa is always fighting really hard, always giving the best on the court.
"He played a very good tournament ... obviously it's very sad for him to finish the way he did."
Cilic has made the semi-finals at Melbourne Park once before, in 2010, when he was beaten in four sets by Andy Murray.
Nadal called for the trainer for the first time down 1-4 in the fourth set and received treatment high on his right leg by the side of the court.
He received further treatment after he lost the fourth set and shook Cilic's hand after he lost his first service game of the final set.
"It's not my hip, but I can't tell you exactly the muscle," a despondent Nadal told reporters.
"It's high on the leg.
"We'll communicate what's going on after I have an MRI (today)."
Cilic will meet British surprise packet Kyle Edmund in the semi-finals after he upset No.3 seed Grigor Dimitrov 6-4 3-6 6-3 6-4.