Novak Djokovic will not defend his title at this year’s ATP Finals as he’s withdrawn from the tournament due to an unknown injury.

The 24-time major champion posted the news to his Instagram story on Tuesday. The ATP Finals begin on Sunday, Nov. 10 in Turin, Italy.

“It’s quite an honor to qualify for the @nittoatpfinals in Turin,” Djokovic wrote. “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. Wishing all the players a great tournament. See you soon!”

Djokovic has won the ATP Finals, which is the end of year tournament somewhat seen as a fifth major, a record seven times. He won the title last year, beating current World No. 1 Jannik Sinner.

It’s possible this isn’t the last we’ll see of Djokovic this season, though. The Davis Cup begins right after the ATP Finals, which is where Rafael Nadal will be retiring from tennis. It’s likely Djokovic will show up, or participate, in order to support his longtime friend and rival.

The other men’s players who qualified for the ATP Finals this year include Carlos Alcaraz, Alexander Zverev, Daniil Medvedev, Taylor Fritz, Casper Ruud, Alex de Minaur and Andrey Rublev.