Novak Djokovic wrote a heartfelt message to Alexander Zverev on Instagram after his injury retirement in the Australian Open.

Alexander Zverev chided the crowd after they booed Novak Djokovic for retiring due to injury after the first set in an Australian Open semifinal.

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.

Alexander Zverev urges fans not to boo Novak Djokovic, who retired in the Australian Open Semifinals due to injury

Novak Djokovic's bid for 11th Australian Open title ends after a muscle tear in his left leg. He says injury happened during match vs. Carlos Alcaraz.

Djokovic is out of the Australian Open after retiring from his semi-final, with Zverev through to face Sinner on Sunday

On Sunday, Alexander Zverev will chase his first Major title against Jannik Sinner in the Australian Open final. The German is through to his third Major final, hoping to lift his first notable trophy. Novak Djokovic backed Zverev to defeat Sinner and join tennis immortals!

A week after a hamstring injury ended his run at the Australian Open, Novak Djokovic, 37, withdrew from Serbia's Davis Cup first-round qualifier, the country's tennis federation said on Tuesday, a move captain Viktor Troicki said has "weakened" the team.

Facing Sinner reminded Alexander Zverev of trying to solve the challenge presented by the 24-time major champion Djokovic.

Novak Djokovic was forced to retire hurt from the Australian Open semifinals - and the Serbian may not be back in action until the French Open.