Rafael Nadal admits top spot is under threat from Novak Djokovic

Rafael Nadal believes there is a good chance Novak Djokovic will replace him as world number one this summer.

Serbian Djokovic stayed unbeaten in 2011 by beating top-ranked Spaniard Nadal in a thrilling Sony Ericsson Open final in Miami.

The Australian Open champion won 4-6 6-3 7-6 (7/4) to pick up his 24th straight win this year, backing up his Indian Wells final win over Nadal a fortnight ago.

"I think he's going to be number one," said Nadal.

"It's difficult for me to say my goal is be number one. My goal is to be competitive in every tournament. If I do that, I'm going to have my chance to be number one.

"He won two tournaments in a row right now, very big tournaments and one grand slam. The normal thing is he will be number one in the next month, month and a half, two months. I don't know. It depends on my results on clay.

"For sure he will be there, no? I'm going to fight for me. If I am solid, if I play a very good clay-court season, we will see what's going on after."

Clay is Nadal's favourite surface and he won four straight tournaments on it last year, including the French Open, but should his performance fall away even slightly this year that would allow Djokovic to take advantage.

Not that the 23-year-old world number two from Belgrade is taking talk of climbing above Nadal too seriously at this stage.

"I know I've had the best start of the season, no question about it. It's the best four months in my life," Djokovic said.

"But it's only the start of the season. I think it's a bit early to talk about getting that top spot in the rankings. Rafa is definitely the best player in the world now.

"If I want to have that shot at the number one ranking, I need to play consistently well throughout the whole year.

"We all know that clay court is his favourite surface, and obviously somewhere where he plays his best.

"But this is going to give a lot of confidence boost for the upcoming clay-court season.

"This streak is incredible that I have, and I want to keep on working hard and try to get more success."

Looking back on the thrilling three-set tussle with Nadal, Djokovic said: "It was one of the closest and best finals that I have played ever."