Marin Cilic advanced to the semi-finals of the Australian Open on Tuesday after top seed Rafa Nadal retired hurt when trailing 3-6 6-3 6-7(5) 6-2 2-0 in their match at Rod Laver Arena.
Nadal took a medical time-out late in the fourth set for treatment on an apparent hip injury and was clearly struggling as he battled on in the evening match.
After being broken to fall behind 2-0 in the fifth, Nadal called it quits, and shook hands ruefully with the chair umpire and Cilic.
Sixth seed Cilic will meet Briton Kyle Edmund for a place in the final.
Cilic reaches Australian Open semi-finals after Nadal retires hurt