Novak Djokovic was absent from the ATP Finals and the Serbian's return to action at the Australian Open could be tougher than first thought.

BELGRADE, Serbia (AP) — Novak Djokovic won’t defend his ATP Finals title after ruling himself out on Tuesday due to an unspecified injury. Djokovic wrote in an Instagram story, “I was really looking forward to being there, but due to ongoing injury I won’t be playing next week. Apologies to those who were planning to see me.”

Earlier this year in Monte Carlo, Casper defeated Novak Djokovic for the first time, toppling the world's leading player and hoping for a similar outcome in Turin on Saturday night. Ruud makes Sinner the favorite, praising the Italian but promising to give his best to perform a stunner.

Jannik Sinner added another big title to his tremendous year, beating US Open runner-up Taylor Fritz 6-4, 6-4 on Sunday for the ATP Finals trophy.

Jannik Sinner opened up about his ongoing doping case after beating U.S. Open runner-up Taylor Fritz 6-4, 6-4 on Sunday to win the ATP Finals trophy before his home fans. Sinner tested positive in two separate drug tests in March,

Jannik Sinner has put together an incredible season of results - and he was compared to Novak Djokovic after his ATP Finals win.

World no.1 Jannik Sinner has capped a remarkable breakout season by winning the ATP Finals on home soil in Turin.