Rafael Nadal has revealed that this season has been the "most emotional" one of his career so far.

Nadal returned from a serious knee injury to regain his spot at the top of the world rankings and win the French Open and the US Open in a successful year for the Spaniard.

However, he could not end it with his first victory at the ATP World Tour Finals in London, losing in straight sets to Novak Djokovic in tonight's final.

"First thing, I want to say is congratulate a super player like Novak. I wish you the best of luck in the Davis Cup, you deserve it," Nadal said in his post-match interview.

"It's been no doubt the most emotional season of my career. To play the last match in this stadium is a fantastic occasion for me even if I didn't have the chance to win today because I played a fantastic player like Novak."

While Nadal is still waiting for his first success in the season-ending tournament, Djokovic has now won the crown two years in a row.