Roger Federer was full of praise for John Isner after the American pulled of a shock Davis Cup victory over the Swiss ace on Friday.
The former world number one had not lost a Davis Cup singles match for nine years but he was beaten in four sets despite taking the opener.
The giant US star bounced back in the second set with one break of serve and, after a tight third set, secured further breaks in the fourth to run out a 4-6 6-3 7-6 (7-4) 6-2 winner in Fribourg.
Federer's defeat was a real set-back for the hosts as Mardy Fish had already upset Swiss number two Stanislas Wawrinka 6-2 4-6 4-6 6-1 9-7 to leave Switzerland with the proverbial mountain to climb to win the tie.
Isner has threatened to take his game to another level over the past few years with some stellar displays.
But he has never really threatened the big four, while remaining in the top 20 in the world.
But he was too good for the 16-time Grand Slam winner on Friday and Federer was gracious in defeat, while stressing that there is still a long way to go.
"I thought he played great - he played it tough and served great when he had to," Federer told a press conference after his defeat. "It's been a difficult day for us, we still have a chance to go through. I'm going to enjoy the challenge."
Federer and Wawrinka will team up for Saturday's doubles against Mike Bryan and Ryan Harrison and must win the rubber to keep the tie alive as a contest.