Rafael Nadal is to miss the Barclays ATP World Tour Finals in London to undergo appendix surgery.
The world number three announced he was suffering from the condition earlier this month but had been managing it with antibiotics.
But, after losing to 17-year-old Borna Coric in the quarter-finals of the Swiss Indoors in Basle on Friday, Nadal announced he was bringing his season to a close.
Speaking to reporters in the Swiss city, the 28-year-old said: "It's the day to say goodbye for the season. I'm not going to play Paris and London. I am not competitive enough to do that."
Nadal will go under the knife on 3 November, six days before the start of the season-ending tournament at the O2 Arena.
