Roger Federer fell to a shock 4-6, 6-3, 7-6 (4), 6-2 defeat by John Isner as the United States took a 2-0 lead against Switzerland in their Davis Cup first-round series on Friday.
Isner's usual big serve was backed by a string of booming ground strokes that challenged third-ranked Federer in longer rallies on the indoor clay court.
Federer's upset loss was even eclipsed for drama and tension by a thrilling opening match as Mardy Fish beat Stanislas Wawrinka 6-2, 4-6, 4-6, 6-1, 9-7.
The U.S. can eliminate Switzerland in Saturday's doubles when a scheduled scratch pairing of Mike Bryan and teenager Ryan Harrison are set to face Federer and Wawrinka, the 2008 Beijing Olympics gold medalists.
A partisan crowd of 7,000 at Fribourg Forum was stunned into silence at Federer's first loss in Davis Cup singles for eight years.
Yet Federer had started in routine fashion, winning the first set without dropping serve.
Isner broke Federer's serve in the sixth game of the second set, but failed to exert any pressure in the third.
Still, Federer couldn't convert break chances in the sixth and eighth games, and the set drifted into a tiebreaker.
Isner never trailed, clinching it on his first set point with a subtle stop volley at the net which gave Federer no chance of retrieval.
The fourth set turned on the fifth game when Isner battled back from 0-40 down with three big serves and two blistering forehand winners.
Federer never recovered and Isner reeled off four straight games, ending the match by rifling a backhand winner crosscourt.
Isner had lost his two previous encounters with Federer, both on hard courts.
AP