Roger Federer made heavy work of his first-round match in his home city tournament in Basel on Tuesday, missing three match points before seeing off American world number 86 Bobby Reynolds 6-3, 6-7, 6-3.
Federer cruised through the opening set but failed to convert three consecutive break points near the end of the second.
Reynolds saved match point on his own serve in the resulting tie-break, going on to win it 8-6, breaking the Federer serve on the final point.
Federer's own service game was never under threat but he again struggled to finish off his opponent, eventually converting the last of five break points to take a 3-1 third set lead.
He missed a further chance to break after hitting a forehand long in Reynolds' next service game and then squandered two more match points when serving at 5-3 before finally wrapping up his win.
"It wasn't easy to get accustomed to the court because I had just two hours' practice on it," Federer said.
"My serve was working well enough though and the fact I never faced any break points myself is something positive I can take from the match."
The world number two will next face the winner of Wednesday's first-round meeting between Argentine Eduardo Schwank and Finland's Jarkko Nieminen -- the man Federer beat to win his second straight Basel title in 2007.
Second seed David Nalbandian and third seed Juan Martin del Potro both enjoyed comfortable first-round wins on Tuesday.
Argentina's Nalbandian beat Spain's Albert Montanes 6-4 6-2, while compatriot Del Potro completed a 6-2 6-4 win over Swiss qualifier George Bastl.
Czech seventh seed Tomas Berdych was less successful, suffering a 6-4 7-5 upset against Italian world number 42 Simone Bolelli.