Even without Rafael Nadal, Spain presents a formidable challenge to the United States' bid to reach the Davis Cup final.
Defending champion Spain welcomes the Americans having won the last two ties between them. Spain hasn't lost on clay, or on home soil, in 13 years.
While the U.S. has won its last four straight ties on clay, Spain has won 25 straight. Singles pair David Ferrer and Nicolas Almagro are a combined 21-1 on the surface, making Nadal's injury absence a minor issue for captain Alex Corretja.
Americans Jon Isner and Sam Querrey are a combined 6-7 on clay going into Friday's opening singles.
"We're a slight favorite," said the 12th-ranked Almagro, who has had to overcome a sore shoulder in recent weeks. "We know about the Americans' great potential. To beat the United States won't be easy, they have a great team, but so does Spain."
The fifth-ranked Ferrer, coming off a U.S. Open semifinal appearance, has had less time to recover and prepare but insists he'll be ready.
"I've recovered from that loss, it was a good tournament for me," said Ferrer, who was ousted by eventual runner-up Novak Djokovic. "I take a very positive reading away from my Grand Slam season, and that's given me a lot of confidence and motivation going into the Davis Cup."
Spain has won three of the last four Davis Cups to become the dominant force in the competition, with a triumph over the U.S. in the 2004 final adding to its first triumph in 2000.
But it can ill-afford to drop any points in singles with Mike and Bob Bryan overwhelming favorites to secure Saturday's doubles point as the pair come off their U.S. Open triumph, which was their record 12th Grand Slam title in the Open era.
Spanish duo Marcel Granollers and Marc Lopez are 1-1 in their first season together, with Lopez also coming off a left leg injury.
The U.S. won on clay both at Switzerland and at France to reach the semifinals, and captain Jim Courier is optimistic about pulling off an upset over the Spaniards.
"We have had the toughest draw you can have in Davis Cup with the road matches we have faced, and this one is the ultimate ask in current Davis Cup tennis," Courier said. "We certainly feel like we're going to have a chance, but we also feel like we're not the favorites. We felt that way in the first two matches this year, too."
Isner has stepped in to fill the hole left by Andy Roddick's departure, with single wins over Roger Federer, Jo-Wilfried Tsonga and Gilles Simon as he swept all four of his singles matchups in 2012.
"He's going to have to be fresh and focused to stand a chance," Courier said.
Spain beat Kazakhstan and Austria to reach the semifinal at Parque Hermanos Castro in Gijon, with the Asturian coastal town hosting Davis Cup for the first time. The teams have split their previous 10 ties, with Spain having won in Austin, Texas, and Madrid most recently.
Reverse singles are on Sunday, with the winner going on to play the Czech Republic or Argentina.
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