Djokovic's 22-match unbeaten run was ended by Karen Khachanov in the Paris Masters final on Sunday after beating Federer in a classic last-four encounter. He added that it has been a complicated year, very good in terms of tennis, but at the same time, very bad as far as injuries are concerned.
He played his last match at the US Open in September, when he retired with a knee injury in the semifinal against Argentina's Juan Martin Del Potro.
Meanwhile, Nadal's place in the ATP finals will be taken by the American, John Isner.
Abdominal problems had seen Nadal pull out of the Paris Masters last week and while they continued to hinder him, the Spaniard also revealed he needed an operation to remove a "free body" from his ankle.
The problem we discovered a very long time, and she would occasionally stop me from playing.
Djokovic beat Nadal in a Wimbledon semi-final thriller before ending a two-year Grand Slam drought by defeating Kevin Anderson in the final.
Monday, November 5, the results of the draw of the Final tournament ATP, which starts in London on 11 November. "However, since the abdominal problem has prevented me from playing in London, we chose to operate on my ankle".
"This way I hope to be in full condition for the next season", he said, and thanked his supporters. But he competed in only three events after the French Open in June.