Andy Murray has withdrawn from the Barclays ATP World Tour Finals in London next month as he continues his recovery from back surgery.
The world number three went under the knife last month and it had been expected that he would not play again this season.
Murray said on atpworldtour.com: "I'm really disappointed not to be playing this year, I love playing in front of my home crowd, it's a great atmosphere.
"All the players look forward to competing in London and I'll be doing my best to qualify again for the tournament next year."
"I'm really disappointed not to be playing this year, I love playing in front of my home crowd"
Murray first began struggling with a back problem during the 2012 clay-court season, and it flared up again on the same surface earlier this year.
The 26-year-old missed the French Open but went unbeaten on grass as he became the first British man in 77 years to win the singles title at Wimbledon.
It was clear, though, that the issue had not gone away, and he was unable to find his best form as his US Open title defence ended in a meek quarter-final defeat by Stanislas Wawrinka.
Soon after it was announced Murray would undergo a minor back procedure in attempt to clear up the problem for the 2014 season.
It is understood Murray's recovery is on schedule, and he saw his surgeon on Monday for the first time since the operation.
Provided he continues to make good progress, he is expected to travel to Miami for his winter training block in the middle of November, around a week earlier than usual.
The Scot considers this period of the year one of his most important, and playing in the World Tour Finals would clearly have risked his preparations for the new season.
Murray has committed to playing an exhibition tournament in Barbados at the end of November and will join Novak Djokovic and Rafael Nadal in Abu Dhabi at the end of December.
Murray's withdrawal is clearly a blow to the World Tour Finals, which has been a huge success since moving to London from Shanghai in 2009.
Tournament director Andre Silva said: "It's unfortunate that Andy will be unable to play in this year's tournament.
"He's had a historic year on the Tour and of course he'll be missed. We wish him all the best as he continues his recovery from surgery and we hope to see him back stronger than ever for the 2014 season."
Nadal, Djokovic and David Ferrer have already qualified for the event, which features the best eight players of the year.
Juan Martin del Potro and Tomas Berdych are well placed to book their places over the next four weeks but the final three spots could go down to the wire.
Roger Federer, Wawrinka and Richard Gasquet currently occupy seventh, eighth and ninth, but Milos Raonic and Jo-Wilfried Tsonga are not far behind.