Former world number one Rafa Nadal admitted he has struggled of late to rekindle his passion for tennis on Thursday after defeat by Jo-Wilfried Tsonga sent him spinning out of the ATP World Tour Finals at the group stage.

Rafael Nadal of Spain reacts after losing a point to Jo-Wilfried Tsonga of France during their singles tennis match at the ATP World Tour Finals in the O2 Arena in London November 24, 2011. [Photo/Agencies]

The 25-year-old Spaniard ended 2010 as the dominant force in men's tennis after completing his career grand slam but apart from a sixth French Open crown in June, this year has been a disappointing one by his sky-high standards.

His 7-6 4-6 6-3 defeat by French powerhouse Tsonga came just two days after he was thrashed in an hour by great rival Roger Federer and the zip and spark is clearly missing from his game.

Nadal, who has played just three tournaments since losing to Novak Djokovic in the U.S. Open final, one of several painful defeats this year by the Serb world number one, offered an explanation in a packed news coneference.

"Seriously I could talk for one hour about that," the 10-times grand slam champion said.

"It's because of lots of things. Because probably I was little bit less passionate for the game, probably I was a little bit more tired than usual.

"I'm happy how I practised the last three weeks. But to compete I wasn't in the right way. We can find excuses, we can find problems, but it's not the moment to say that."

"In your career you have moments where you come back, then you go down. Today is not my best moment."

While one grand slam title and defeats in the Wimbledon and U.S. Open finals would be rated as a massive achievement by mere mortals, 2011 will certainly not be one he looks back on particularly fondly.

However, he said after trying to win the Davis Cup for Spain in Seville next weekend he would get himself ready to come back firing at the Australian Open in January.

"I'm going to continue with the right practice like I had the last three weeks," he said.

"That's the only way to try to arrive to the 2012 season. I'll try to arrive in 2012 in very good condition. I'm going to do all I can to be perfect for the beginning of 2012.

"This end of the year wasn't easy for me. That's hard to accept. But at the same time that's given me little bit more desire and a little bit more of a goal for 2012."

Nadal said he was not worried about his form going into the Davis Cup final against Argentina, a tie that will be played on his favoured clay.

"On clay I have more time to think. The movements are a little bit easier for me," he said.

"I will try my best every day to try to win the Davis Cup for my country. I'm lucky, the team, not only myself, if I'm not in the right conditions, the captain can choose another player."