Spectators booed as the 37-year-old Djokovic walked off toward the locker room, and he stopped, turned around and responded by giving two thumbs-up.

Zverev will face defending Australian Open champion and No. 1 seed Jannik Sinner, who beat American Ben Shelton 7-6 (2), 6-2, 6-2, in Sunday's final. Zverev is pursuing his first major tournament title.

Novak Djokovic is out of the Australian Open in stunning fashion. The 24-time slam champion medically retired immediately after dropping the first set of his semifinal match against No. 2 Alexander Zverev in a tiebreak 7-6 (5).