Radek Stepanek rallied to beat Viktor Troicki 4-6, 6-2, 6-4, 6-4 and give the Czech Republic a 1-0 lead over Serbia in their Davis Cup semifinal on Friday.
Troicki was a late replacement for Serbia's top player and U.S. Open runner-up Novak Djokovic.
''I learned today that I would play. I was ready because I knew that Djokovic wasn't and I was focused, but it's different when you are not sure you are going to play,'' Troicki said.
Djokovic officially pulled out because of gastroenteritis, but told reporters he was still too tired after only returning to the Serbian capital on Wednesday, two days before the match.
Djokovic, who watched part of the match from Serbia's box, added that he might yet play in the doubles.
''I decided to keep my strength for the last two days,'' the second-ranked Djokovic said. ''If the result after the first day requires it, I might play the doubles on Saturday too.
''But I will surely be ready for Sunday.''
Djokovic lost to Rafael Nadal on Monday, in a rain-delayed U.S. Open final. He needed five long sets to beat Roger Federer in the semifinals and then played four against Nadal.
''I am still very tired from the tough matches at the U.S. Open and the long trip back home. I told Troicki the day before to be ready to play against Stepanek,'' Djokovic said.
Troicki looked ready in the first set, breaking serve in the opening game.
But the experienced Czech gained the upper hand in the second set, changing pace with frequent drop shots and forcing Troicki into errors.
''I was very surprised that Djokovic didn't play,'' Stepanek said. ''I only learned three hours before the match that he wasn't playing. I had to change my game plan quickly.''
''I managed to break serve in the second set and I turned the match. I won a few straight points at the end of the third and that was the key.''
Despite loud support from some 15,000 fans, Troicki was unable to pick up his game and was too erratic to give Serbia a vital point despite breaking serve for a 3-2 lead in the fourth set. Stepanek broke right back and clinched the match on another Troicki error.
Troicki had 20 aces for Stepanek's eight, but the Serb also had 50 unforced errors, 14 more than Stepanek.
''This was one of the worst defeats in my career,'' Troicki said. ''It's tough to lose in front of your hometown crowd.''
''I beat him twice easily this year, but it was on a different surface. I was under a lot of pressure here. I had a little slump in the second set and he took advantage of it,'' Troicki said.
Stepanek went into the match with a 3-2 career record against Troicki, but the Serb had won the last two in straight sets at U.S. tournaments this year.
Stepanek played little this year because of a left-knee injury and mononucleosis. He was once ranked in the top 10, but has dropped to No. 35, while Troicki is No. 47.
''I haven't had a great year but the Davis Cup has a special place in my heart,'' Stepanek said.
Serbia is seeking to reach its first Davis Cup final, while the Czech Republic was last year's runner-up to Spain.
In the second singles, Wimbledon runner-up Tomas Berdych plays Janko Tipsarevic of Serbia.
