Roger Federer of Switzerland reacts after losing his Davis Cup tennis match against John Isner of the U.S. in Fribourg February 10, 2012. [Photo/Agencies]

MADRID - John Isner shocked Roger Federer in four sets to secure a 2-0 lead for the United States away to Switzerland in Davis Cup World Group action on Friday while holders Spain carved out the same advantage over Kazakhstan in their first-round tie.

Big-serving Isner beat Federer 4-6 6-3 7-6 6-2 to end his opponent's 15-match unbeaten run in Davis Cup singles rubbers and described it as the greatest win of his life.

He had lost his two previous meetings with the Swiss, both on hardcourts, but this time the 17th-ranked Isner spoiled a rare Davis Cup appearance by the 16-times grand slam singles champion with a clinical performance on clay in Fribourg.

John Isner of the U.S. reacts during his Davis Cup tennis match against Switzerland's Roger Federer in Fribourg, February 10, 2012.  [Photo/Agencies]

"It's one of the greatest wins of my life, no that's wrong, it's the greatest win of my life," said Isner at courtside after the two-hour 39-minute contest.

Mardy Fish had earlier edged Stanislas Wawrinka 6-2 4-6 4-6 6-1 9-7 as Switzerland's bid to reach the quarter-finals for the first time since 2004 got off to the worst possible start against the team that beat them in the 1992 final.

"The mission was to go out there and not allow an artist a canvas to work with," US captain Jim Courier said of Isner's victory.

The winners of the tie will play away in the last eight against Canada or France who were playing later on Friday.

Spain began the defence of their title with Nicolas Almagro, their number one in the absence of Rafa Nadal and David Ferrer, and Juan Carlos Ferrero winning in contrasting fashion.

Almagro, had a fairly comfortable 6-3 4-6 6-1 6-1 victory over stubborn Kazakh Andrey Golubev while Ferrero returned to the Davis Cup with a thrilling 6-1 4-6 7-6 4-6 6-4 win over Mikhail Kukushkin in a gruelling four hour 28 minute contest.

Packed Calendar

Last year's runners-up Argentina took a 2-0 lead against Germany after David Nalbandian and Juan Monaco saw off Florian Mayer and Philipp Petzschner respectively on Bamberg's indoor clay court.

Monaco dismissed Petzschner 6-3 6-3 6-3 as the U.S. Open doubles champion committed 47 unforced errors in a disappointing performance before Mayer lost 2-6 6-0 6-1 7-6 to Nalbandian.

In Hyogo, Japan's Go Soeda, the world number 90, came from two sets down to upset 55th-ranked Ivan Dodig 6-7 3-6 6-4 6-3 7-5 and open a 1-0 lead over Croatia.

Ivo Karlovic then levelled for the 2005 champions with a 6-4 6-4 6-3 success against Kei Nishikori.

Serbia, the 2010 winners who are without world number one Novak Djokovic, are 2-0 up at home to Sweden thanks to a 6-3 6-3 6-4 victory for Janko Tipsarevic over Filip Prpic and Viktor Troicki's 6-4 6-3 5-7 6-3 triumph over Michael Ryderstedt.

Austria hold a 2-0 advantage over Russia after Juergen Melzer fought off Igor Kunitsyn in five sets and Andreas Haider-Maurer beat Alex Bogomolov in four in Wiener Neustadt.

Czech Republic also have a 2-0 lead over Italy thanks to Radek Stepanek's battling 4-6 6-4 6-3 3-6 6-3 win over Andreas Seppi and Tomas Berdych's 6-3 4-6 7-5 6-2 victory against Simone Bolelli.

Packed Calendar

Spain captain Alex Corretja was unable to call on any of the four players who beat Argentina in last year's final as Ferrer, Feliciano Lopez and Fernando Verdasco all joined Nadal in stepping aside.

World number two Nadal, who has never lost on clay in 16 Davis Cup singles rubbers, blamed the packed calendar for his decision to opt out this year and Corretja drafted Ferrero back into the team after an absence of more than two years.

The former world number one, who turns 32 on Sunday and is now ranked 48th, did not disappoint the typically raucous Spanish fans but had to come back from a break down in the deciding set against the 61st-ranked Kukushkin.

"I tried to stay in the match by keeping my calm and attacking more," said Ferrero, who needed strapping on his right thigh after the third-set tiebreak.

"I did not expect such a long match but in the end I made the effort and I think it was worth it," the 2003 French Open champion said in a television interview. "Winning a point for Spain in the Davis Cup is always very emotional."