LONDON – Argentina’s Juan Martin del Potro, who pulled off the biggest surprise of the tennis season by winning this year’s U.S. Open, said he still needs more experience before he can be considered a favorite for big events like the season-ending Barclays ATP World Tour Finals, which gets underway here Sunday.

“I need to get more experience. I have to learn much to be like them,” the 21-year-old told London daily The Independent, referring to 15-time Grand Slam champion Roger Federer of Switzerland, six-time Slam champ Rafael Nadal of Spain, Scotland’s Andy Murray and Serbia’s Novak Djokovic.

Del Potro, who is ranked just behind those players at No. 5, shocked the tennis world in September by coming from behind to defeat Federer in five sets at the U.S. Open in New York and capture his first-ever Grand Slam title.

But his results since then have been patchy, perhaps because he is worn out after a long and eventful season.

Del Potro lost in the first round at a tournament in Tokyo, withdrew because of injury during his first match at the Shanghai Masters and then withdrew during his quarterfinal match at the BNP Paribas Masters last week.

The native of Tandil, about 150 miles southwest of Buenos Aires, reflected on the outpouring of support he received from his hometown fans after winning the U.S. Open.

“I was driven around the city on top of a fire engine,” he said. “It was scary, but it was also the best moment of my life. Everyone came out on to the streets and I felt very happy. I feel very happy whenever I go back to Tandil. It’s very important to me.”

Del Potro is making his second straight appearance in the eight-man, year-end championships and this time around his group in the round-robin phase also includes Federer, Murray and Spain’s Fernando Verdasco.

In the interview, Del Potro expressed his appreciation for his first coach, Marcelo Gomez, who also helped develop other ATP players such as Juan Monaco, Maximo Gonzalez and Diego Junqueira.

“When I was young I travelled with him and he was like another father to me. That’s very important when you are young. My parents are friends with him and I still speak to him every day. He’s a very good person. I spoke to him before the U.S. Open final,” Del Potro said.

The Argentine has rocketed up the rankings over the past year-and-a-half, climbing from No. 81 by winning four tournaments in a row in the second half of 2008 and consistently reaching the semis and finals of big tournaments this year.

One of the places where Del Potro has struggled thus far in his career is at tennis’ most prestigious event, Wimbledon, but he said he is committed to improving his grass-court game.

“I don’t play good tennis there, but I will learn because I love Wimbledon,” he said. “I’d like to play good tennis on grass. It’s difficult, but if (2001 champion Goran) Ivanisevic and (2008 semifinalist Marat) Safin can play on it, maybe I can too.”

Del Potro used to play soccer when he was growing up and remains close friends with several of Argentina’s top players, including Carlos Tevez, Javier Mascherano, Emiliano Insua, Lionel Messi, Sergio Aguero, Mauro Camoranesi and Lucho Gonzalez.

“I love soccer, but I never thought seriously about being a professional,” he said.

Judging by all the success he’s achieved at such a young age, it appears Del Potro was wise to choose tennis instead. EFE