Musetti was 6-4 6-3 up and looked set for the semi-finals when he pulled up early in the third set. It is another stroke of luck for Djokovic after fourth-round opponent Jakub Mensik withdrew before their scheduled match with injury. Two-time defending champion Sinner had some physical struggles but was good enough to beat Ben Shelton 6-3 6-4 6-4 in the other quarter-final. After breaking Musetti and getting out to a 30-0 lead on serve, Djokovic hit five unforced errors in six points to hand the initiative back. Anchored by a one-handed backhand that kept Djokovic guessing and an improved serve, Musetti held off his opponent to move within touching distance of a first Australian Open semi-final.