Injured Tsitsipas pulls out of ATP Finals

Stefanos Tsitsipas (right) reached this year's Australian Open final

Stefanos Tsitsipas retired because of injury after three games of his ATP Finals match against Denmark's Holger Rune.

The Greek world number six appeared to be troubled by a back problem and left the court to a few jeers from the crowd inside Pala Alpitour in Turin, Italy.

His withdrawal from the match means he cannot progress to the semi-finals.

Novak Djokovic is now able to book his spot in the last four with a win over Jannik Sinner later on Tuesday.

If Tsitsipas officially withdraws from the ATP Finals, then number one alternate Hubert Hurkacz will replace him for his final match against Djokovic.

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