The Spaniards were favorites ahead of their Davis Cup World Group semi-final against the U.S. and David Ferrer's opening singles victory against Sam Querrey cemented their position. But it was it was Nicolas Almagro's marathon win over John Isner that gave the Spaniards the undisputed advantage.
Spain now needs just one win in the five-match affair to enter the final.
World number five David Ferrer came from a set down to get past Sam Querrey 4-6, 6-2, 6-2, 6-4 before Nicolas Almagro won a four-hour long marathon match against American John Isner, 6-4, 4-6, 6-4, 3-6, 7-5 in the Spanish port city of Gijon on Friday.
"It was a hard match, difficult at every moment," 30-year-old Ferrer said after his win.
Ferrer came back from the first set loss to outfox 26th ranked Querrey. All this despite the fact that Ferrer had little time to recover post his U.S. Open semi-final loss to World No. 1 Serbian Novak Djokovic.
"It was a very tough match throughout, he didn't make it easy for me," Ferrer told Spanish television.
However, it was Almagro, who had to fight off stiff resistance from Isner, known for his liking for marathon matches.
The 10th-ranked American had saved three match points in the ninth game of the deciding set. Eventually he succumbed to the persistence of the 12th ranked Almagro.
"That was really disappointing because I did such a good job the whole fourth and fifth set of just hanging in there and I just kind of gave it away at the end," Isner told reporters after the match.
Ferrer, who is leading the home-team in the absence of injured Rafael Nadal, certainly has a record to boast of -- 15 wins in 15 Davis Cup singles rubbers on clay. Overall it was the 30-year-old's 20th victory in 24 matches.
Spain are bidding for a fourth Davis Cup crown in five years, while the U.S., without the services of Andy Roddick, who retired at the end of the U.S. Open, have not won the competition since 2007.
The winner of the tie will either meet Argentina or Czech Republic, who are busy playing in the second World Group semi-finals in Buenos Aires where the two teams are tied 1-1.
Tomas Berdych overcame a determined Juan Monaco 6-1, 4-6, 1-6, 6-4, 6-4 to pull the Czechs level after world number eight Juan Martin del Potro had given the Argentines the lead with a straightforward 6-4, 6-4, 6-2 victory over Radek Stepanek.