Wimbledon, July 3 (IANS) :Spanish tennis ace Rafael Nadal says he may not be able to return to his heydays in Wimbledon after he was knocked out from the competition in the second round by German qualifier Dustin Brown.

The world number 10, lost 5-7, 3-6, 6-4, 6-4 to world No.102 Brown as his dismal run in the tourney continued. The 29-year-old has been beaten by players ranked outside the top 100 in each of his last four appearances at Wimbledon.

"I don't know if I will be back to the level of 2008, 2007, 2006 or even 2011," said Nadal.

"My motivation is to be back to that level. I want to keep working hard. But If I don't make that happen then I've played five finals and taken the trophy back home two times, so that's not bad," the 14-time Major champion said at the post-match press conference on Thursday.

Nadal was defeated in the quarter-finals at both the Australian Open and French Open earlier this year. However, he insists he is not finished yet.

"It is not the end. It's a sad moment for me but life continues. My career, too. I will keep going," he said.

The Spaniard also added he was fit and ready for the competition this year after struggling with a knee injury in 2012-13.

"In 2012 and 2013, I know I was not competitive. I had problems with my knees before but this year there wasn’t any such problems. I was ready to compete," 2008 Olympic champion Nadal said.

"I had the right preparation, all the things I thought were going to be fine to play a good Wimbledon."