NEW YORK (Reuters) - Rafa Nadal will lead the Spanish Armada into the fourth round of the U.S. Open on Tuesday as he continues his bid to capture the only grand slam to have eluded him.
Spain have strength in numbers and are already assured of having at least one men's semi-finalist after filling all four remaining spots in the top quarter of the draw.
The four, Nadal, Fernando Verdasco, David Ferrer and Felciano Lopez, are all seeded and close friends after teaming up to help their country win the Davis Cup last year and earn the nickname the La Armada Invencible (The Invincible Army).
Nadal is looming as the obvious favorite to advance after getting through his first three matches without dropping a service game but first he must get past Lopez, the 23rd seed, in Tuesday's late night match at Arthur Ashe Stadium.
Verdasco, seeded eighth, and Ferrer, the 10th seed, will square off at Louis Armstrong Stadium while a fifth Spaniard, the unseeded Tommy Robredo, is also in action at Louis Armstrong, playing Russia's Mikhail Youzhny.
"Already one Spanish player going to be in semi-finals, that is positive news for us," Nadal said.
"Especially because the ball and the court is probably the most difficult tournament for us, so that is very important news for Spanish tennis."
The host nation's chances of winning either championship will go on the line when the last remaining Americans, Venus Williams and Sam Querrey, play the two day matches on center court.
Querrey will play Switzerland's Stanislas Wawrinka, who upset Britain's Andy Murray on Sunday, for a place in the quarter-finals, while Williams faces Italy's French Open champion Francesca Schiavone.
Williams has won all seven of her previous matches with Schiavone but had to come from a set down to win their last two.
"Obviously her game is better than ever now," Williams said. "I'm hoping that my experience will help me."
Defending women's champion Kim Clijsters faces a tricky quarter-final against Australia's French Open runner-up Samantha Stosur.
Clijsters is on an 18-match winning streak at Flushing Meadows, that includes winning the 2005 and 2009 titles, and has won all three of her previous meetings against Stosur.
But the Belgian remains wary about the dangerous fifth seed, who is one of the biggest hitters in the women's game and developing a reputation as a great fighter.
"Sam is a different player than what she was a few years ago," Clijsters said. "She's definitely improved a lot."
Stosur saved a break point to beat world number one Serena Williams in Paris in June and saved four match points against Elena Dementieva to win their fourth-round match in New York that did not end until 1:35 a.m. Monday, the latest finish for a women's match at the U.S. Open.
"She's got a good 14 hours headstart recovery on me. She played first. I played last," Stosur said.
"It's just one of those things. I'm going to have to play well, play some of my best tennis probably and really fight hard and go for it."
Editing by Steve Ginsburg