Roger Federer and Stanislas Wawrinka lost the doubles match to Andrey Golubev and Aleksandr Nedovyesov on Saturday in Genbeva, Swirtzerland, giving Kazakhstan a 2-1 lead over the Swiss in the Davis Cup quarter-finals.
Golubev and Nedovyesov never trailed after breaking Federer in the opening game and completed a 6-4, 7-6 (5), 4-6, 7-6 (6) victory.
The Kazakh pair converted their first match point when Wawrinka could not control Golubev's powerful return of Federer's serve.
"Against those guys you have to play almost the perfect match. I'm happy that we did today," Golubev said.
Federer and Wawrinka, the Australian Open champion, won gold in doubles at the 2008 Beijing Olympics and were loudly supported by the 16,000 spectators in the indoor Palexpo arena.
"Pretty excited, especially that we beat the Olympic champions. It makes it special," said Nedovyesov, who is ranked No. 76 in singles.
In Sunday's reverse singles, No. 3-ranked Wawrinka is scheduled to play the 56th-ranked Mikhail Kukushkin before Federer takes on the 64th-ranked Golubev, who beat Wawrinka in Friday's opening singles.
The winner plays Britain or Italy in the semifinals in September.
The Swiss were a service break up in the second set, but the Kazakhs broke back when Wawrinka served for the set at 5-3.
The visitors clinched a two-set lead when Federer sent a half-volley wide as he approached the net.
Federer and Wawrinka served out the third set after breaking in the fifth game.
Federer's serve came under pressure again in the fourth set, trailing 0-30 when down 6-5 before forcing the tiebreaker. Switzerland held a set point but Federer's backhand lob drifted long.
Murray, Fleming lead Britain to 2-1 lead
Britain held off a comeback attempt from Italy to win the doubles match and take a 2-1 lead in their Davis Cup quarterfinal.
Andy Murray and Colin Fleming beat Fabio Fognini and Simone Bolelli 6-3, 6-2, 3-6, 7-5 in three hours to boost Britain's bid to reach the semifinals for the first time since 1981.
Earlier, Murray completed a 6-4, 7-5, 6-3 victory over Andreas Seppi in their delayed singles match.
Britain looked on course for a straight-set victory but the Italian duo saved four break points at the start of the third set and went on to get a foothold in the match. Italy has not lost at home to Britain since 1926 and is hoping to reach the semifinals for the first time in 16 years.
France trails Germany
Julien Benneteau and Michael Llodra held their nerve to beat Andre Begemann and Tobias Kamke 6-1, 7-6 (5), 4-6, 7-5 as France pulled back to 2-1 in their Davis Cup quarterfinal against Germany.
The French were under huge pressure after 12th-ranked Jo-Wilfried Tonsga and Benneteau lost their opening singles games on Friday against much lower-ranked opponents.
Germany opened up a 3-1 lead in the fourth set but the experienced French veterans stood up to the challenge, breaking back for 3-3.
They sealed victory on the third match point when Llodra chopped back Begemann's serve and the German player could only pat the ball back into the net as he lunged forward.
France needs to win both reverse singles on Sunday to progress to the semifinals.