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.

Djokovic, who retired due to injury after the first set, was booed by the crowd as he walked off Rod Laver Arena.

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).

Novak Djokovic retired injured after losing the first set 7-6(5) against Alex Zverev on Friday to put the German through to his first Australian Open final.

Novak Djokovic retired due to injury after losing the first set to Alexander Zverev 7-6 (5) in the semifinals of the Australian Open on Friday. Zverev

Parts of the crowd at Rod Laver Arena booed Novak Djokovic when he medically retired from his Australian Open semifinal clash against Alexander Zverev on Friday.

Novak Djokovic has heartbreakingly revealed he thinks Australian Open fans 'don't want to understand' him following his withdrawal from the tournament on Friday. The tennis icon was forced to pull out due to injury after losing the first set to Alexander Zverev,

An injured Novak Djokovic quit because of a torn muscle in his left leg after dropping the first set of his Australian Open semifinal against Alexander Zverev on Friday. Djokovic lost the opener 7-6 (5) and immediately walked around the net to concede the match to Zverev and shake hands.