Rafael Nadal confirmed on Monday he will miss the ATP Finals in London this month and that his season is over due to injury.
Nadal said he needed an operation on his right ankle and is also yet to recover from the abdominal problem that kept him out of the Paris Masters last week.
It means Novak Djokovic is guaranteed to end the year top of the world rankings while John Isner, the world number 10, comes into the field for the ATP Finals on Sunday.
"I am writing to you to signal the end of the season," Nadal said.
"It has been a complicated year, very good in terms of tennis when I was able to play and very bad in terms of injuries."
"In this way I hope to be in full condition for the next season."