Defending champion Novak Djokovic pulls out of the ATP Finals because of injury, a move which sets the eight-man field for the event.

Citing an unspecified, "ongoing injury," Novak Djokovic announced his withdrawal from the season-ending ATP Finals on Tuesday.

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.”