The Serbian superstar won his 101st ATP title after defeating Italian Lorenzo Musetti 4-6, 6-3, 7-5 in a hard-fought three-hour battle on Saturday.
However, Djokovic announced that he will skip the ATP Finals in Turin despite qualifying for a record equalling 18th time in his illustrious career.
"I was really looking forward to competing in Turin and giving my best," posted the 38-year-old on his social media.
"But after today's final in Athens, I'm sad to share that I need to withdraw due to an ongoing injury."
The decision means Musetti will replace Djokovic at the ATP Finals despite the loss in Greece denying him an automatic qualifying spot.
"After yesterday's [Friday] match, I was hoping that it was not going to flare up. But then today, even before the match, it was not great. I had to take all the strong medications to be able to play the match, " added the Serb to reporters.
"I felt there's no chance for me to go through the entire tournament in Turin with the required level of tennis when you're playing the best eight in the world."
Djokovic is now two titles away from equalling Roger Federer's tally of 103, with Jimmy Connors leading the list of legends with 109 tournament victories.