Rafael Nadal insists he will be able to recharge his batteries in time to help Spain win their Davis Cup final showdown against the Czech Republic next week.

Nadal limped out of the ATP World Tour Finals on Friday after losing 7-6 (7/5), 6-3 to defending champion Novak Djokovic.

Rafael Nadal of Spain plays against Novak Djokovic of Serbia during the Barclays ATP World Tour Tennis Finals in London. -AFP

It was the world number two's third successive defeat at the season finale and meant he departed London's O2 Arena without winning a single set.

Nadal concedes that he is feeling the strain of a gruelling and traumatic campaign that has been scarred by injuries to his knee and abdomen, as well as the separation of his parents.

But, while the rest of his rivals will leave the English capital for a well earned break, Nadal, who suffered a back injury against Djokovic, heads to Barcelona to spearhead Spain's challenge to win the Davis Cup from December 4-6.

The 23-year-old believes the prospect of playing his part in a Spanish victory will be enough for him to summon up one final push from his weary limbs.

"My battery is finished," he said when asked how he felt. "Sometimes they finish and you have to buy another one!

"Only practising will help you come back to your best level. That's what I did all my life. I gonna still do it.
"When you feel better physical, you can play more aggressive because you are not feeling tired after points. That's important.

"I know it is going be a difficult final. The change to clay from hard courts is going to a big change. It's always difficult in the beginning.

"That's a big motivation for me, finish the year winning. And I have the opportunity to play well, to play good tennis on clay, and to win something important for my country and for my friends.

"We are confident. If we are playing well, we have a good chance. "But the Czech players play well on clay too. we know how tough it is going to be in the final. We know the Czech Republic wants to win the Davis Cup, too."

Nadal is adamant playing in the Tour Finals was a worthwhile learning experience, even though he arrived in London already low on energy.

Although he started the year in blistering form, winning the Australian Open for the first time, Nadal was unable to defend his Wimbledon crown due to injury and has struggled to recapture his best form since then.

"I only want to forget the tournaments that I didn't play because of the injuries. For the rest, every tournament is important," the four-time French Open champion said. "Anyway, if you lose, you have to learn. This tournament has given me the opportunity to see what I have to do to play better and to start the next year better.

"I have seen what I have to do if I want to be more competitive on these kind of surfaces. "I have to be more aggressive on the first shot. After the serve, when I hit the first forehand, I have to attack more than I did in the last months.

"When you have less confidence it is more difficult to do it. But the confidence is going to come back."