NEW YORK, September 1, 2009 (AFP) - At 6 feet 6 inches (1.98m), Sam Querrey is too big for Grand Slam glory, according to many observers, but the giant American believes the times are a changing.

Nowadays height, within reason, is no obstacle, he believes, and the 21-year-old Californian who many believe will one day take over from Andy Roddick as his nation's flag-bearer says the evidence is all around.

"Athletes are evolving in all sports," he said.

"You look at the NBA. Every guy is between 6'5" and 6'10" and they're fast and quick. Same with (American) football players.

"You're seeing it in all sports, bigger athletes are becoming quicker.

"It's not just the guys who are 5'8", 5'9". You're seeing a lot of guys over 6'5" who are quick in tennis, football, basketball, you name it.

"The science behind training is betere. I think that has a lot to do with it."

Querrey, who reached the US Open second round with a 6-3, 7-5, 6-4 win over compatriot Michael Yani, says the platform for his success over the last few

weeks, during which he won at Los Angeles and was runner-up at Newhaven, Newport and Indianapolis, was built during the spring on the clay courts of Europe.

The slow, red stuff is most definitely his least best surface, but Querrey, like others before him, understood that it is excellent for nurturing stroke-making skills and endurance.

"The clay court season, I didn't win a lot of matches, but I still felt like I played well," he said.

"I think it's good to go over in Europe and play for eight weeks and learn to play on clay. I probably won just three matches but I felt good about my game after that."

Now the second-ranking American at 22 in the charts, Querrey says although he does not feel the pressure of public expectation he knows that the time has

come when he has to step up another notch and put himself in with a chance of winning a Grand Slam tournament.

"You look at Roddick who won a slam at 21. Nadal at 18, 19, 20, 21. Djokovic last year was 21, maybe 22 at the Australian. Murray is right there. He's 22.

So, I mean, a lot of guys have done it at a young age," he said.

Querrey also has his own ideas of how to increase the public appeal of tennis, including allowing fans to cheer during points, saying that players should be professional enough to simply ignore the din.

"A lot of guys are going to wait till every single person sits down. You're just kind of like, no wonder tennis isn't as popular as football, basketball, baseball, soccer," he said.

"I think if fans had a little more leeway to yell and cheer, it might increase the popularity a little bit."