Wimbledon Open: Rafael Nadal Worried By First-Round Foe, as Andy Murray, Roger Federer & Novak Djokovic Await

Rafael Nadal of Spain puts on a headband during his men's singles match against Robby Ginepri of the U.S. at the French Open tennis tournament at the Roland Garros stadium in Paris May 26, 2014. REUTERS

World's number one Rafael Nadal doesn't underestimate his first-round opponent at the Wimbledon Open. In fact, he even sounded quite scared of Martin Klizan during an interview after a practice session on Saturday.

Nadal, who hasn't won a single grass-court match since 2012, is bracing for a tough match against the 57th-ranked Klizan.

The 28-year old Spaniard had a nightmarish stint in his last two campaign at Wimbledon, lossing to Lukas Rosol in the second round of the 2012 Wimbledon and Steve Darcis in the first round last year. He was also obliterated by unheralded Dustin Brown in the early round of Halle tournament.

Aware of the peril of early round hiccups, Nadal stressed he would take things one step at a time, as he tries to improve from his miserable outing the last two years.

"I don't see farther than today. I have a tough first round against Klizan. For the last two years I lost in the first and second round. I start from the first round in every surface. You can imagine even more here on grass," said Nadal via Tennis Tonic.

"Personally I feel that I am doing things better. It is true that for the last couple of years I didn't play lot of matches on grass, but I am confident that I can do it again. I am not talking about winning, rather talking about play better than what I did the last couple of years on grass."

Still despite possibly facing Novak Djokovic, Andy Murray and Rofer Federer in their tip-top forms, the Mallorcan Bull is optimistic about his chances in this tournament, believing the improvement in his knee this year has helped him to become comfortable on fast surface (grass).

"After winning Roland Garros last year, probably emotionally, I went down a little bit after that. Last year, I was not 100% ready for the grass. I knew my knee was not perfect yet and grass is very aggressive for my knee because I need to play very low," Nadal said in an interview with the Guardian.

"But this year is a different story. Overall the feeling this year is better with my knee. I feel a little more comfortable running, and that's very important."

Nadal is gunning for his third Wimbledon Championships, having won the prestigious title in 2008 and 2010.