Rafael Nadal has helped his nation cure its longtime aversion to lawn tennis, and he'll be one of three Spanish men playing today in the fourth round at Wimbledon.

Switzerland, France, Russia and Croatia have two players apiece among the final 16. Britain - which last won the men's singles title in 1936 - advanced one man to the second week, as did Australia, Germany, Serbia and even the island of Cyprus.

And the United States? None.

The nation that produced Andre Agassi, Don Budge, Jimmy Connors, John McEnroe, Pete Sampras and Bill Tilden finds itself in a collective slump. And there's no sign of a turnaround.

"We've been struggling for a long time, and it has just gotten worse," said Gene Mayer, a former top-five player who coaches privately in New York.

So far Wimbledon has been jolted by a series of first-week upsets that decimated the seeding lists.

Six of the top-10 seeded men were knocked out before the fourth round: No. 3 Novak Djokovic, No. 4 Nikolay Davydenko, No. 5 David Ferrer, No. 6 Andy Roddick, No. 7 David Nalbandian and No. 9 James Blake.

Among the women, two of the top three-seeded players are out - No. 1 Ana Ivanovic and No. 3 Maria Sharapova.

For the first time since 1926, only one US male - No. 102-ranked Bobby Reynolds - reached the third round at Wimbledon. He lost on Friday.

The problem isn't grass. At last year's French Open, American men went 0-9, their worst showing on the Roland Garros clay in at least 40 years. The last US male to win a major title was Roddick at the US Open in 2003.

The drought is less noticeable on the women's side only because of the Williams sisters, who have combined for 14 major titles. They and Bethanie Mattek were the lone Americans to survive the first week at Wimbledon.

Venus and Serena Williams will play their fourth-round matches back-to-back today on Court 2 - nicknamed the "Graveyard of Champions" for its history of upsets of Wimbledon winners.

Not only that, the sisters are scheduled to play doubles on the same court the same day.

Between them, the sisters have won six of the last eight women's Wimbledon singles titles. Defending champion Venus is a four-time winner, and Serena is a two-time champ. Venus will be up first against 18-year-old Russian Alisa Kleybanova, with Serena following against Mattek. Later, they will team up in doubles against Anabel Medina Garrigues and Virginia Ruano Pascual.

While development flounders in the US, waves of talented youngsters keep surfacing in Europe, Asia and South America. Ricardo Acuna, a national coach for the US Tennis Association, said Americans are winning less because the game has gone more global. "More than it's a drought, it's that the world got better," said Acuna, a former top 50 player.

(Agencies via Shanghai Daily June 30, 2008)