Novak Djokovic of Serbia gestures during the semifinal match against Jannik Sinner of Italy at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)

Jannik Sinner of Italy hits a return to Novak Djokovic of Serbia during their semifinal match at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)

Novak Djokovic (R)of Serbia receives medical attention during the semifinal match against Jannik Sinner of Italy at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)

Novak Djokovic (L) of Serbia and Jannik Sinner of Italy pose for photos ahead of their semifinal match at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)

Novak Djokovic of Serbia returns the ball to Jannik Sinner of Italy during their semifinal match at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)

Novak Djokovic (R) of Serbia greets Jannik Sinner of Italy after their semifinal match at the Six Kings Slam exhibition tennis tournament in Riyadh, Saudi Arabia, Oct. 17, 2024. (Xinhua/Luo Chen)