Nadal pulls out of ATP World Tour Finals

Former runner-up Rafael Nadal pulled out of next month's season-ending ATP World Tour Finals, citing a left knee injury.

It was previously announced that Nadal would not return to action until an exhibition tournament in Abu Dhabi in late December. The former No. 1 star and current world No. 4 has been sidelined since June when he was shocked by unheralded Czech Lukas Rosol in the second round at Wimbledon.

Nadal, who has a partial tear of the patella tendon in his knee, will also miss next week's Paris Masters event.

The reigning French Open titlist and 11-time Grand Slam singles champion was unable to defend his Olympic title in London and also missed the U.S. Open last month.