Little separated Nadal and big-hitting Cilic until the injury struck, as they traded ferocious groundstrokes in an intense battle. But the Spaniard, who was beaten in last year's final by Roger Federer, called the physio at 1-4 in the fourth set and again at the changeover when two sets apiece and the writing was on the wall. "It was an unbelievable performance from both us," said Croat Cilic, the sixth seed. "It is really unfortunate for Rafa to finish this way." Nadal's retirement follows the departure on Monday of Novak Djokovic, with his immediate playing future uncertain after an elbow injury flared. He also appeared to have a hip problem.
"Really unfortunate for Rafa. He is an unbelievable competitor. Always gives his best and it's very unfortunate for him to finish this way. " - @Cilic_Marin will play @Kyle8Edmund in the SF. Kudos to the ?? on a superb performance nonetheless. #AusOpen pic.twitter.com/rMFIW9Wl4a— #AusOpen (@AustralianOpen) January 23, 2018