Local favourite Patty Schnyder eased into the second round of the Zurich Open on Tuesday after sixth seed Serena Williams retired injured at 6-0, 3-0 down.
The American, who lost Sunday's Kremlin Cup final to Elena Dementieva, looked extremely out of sorts, barely moving as she surrendered her first two service games.
Briefly leaving the court at 3-0 down, Williams returned but showed no sign of improvement, taking just three more points as Schnyder romped through the opening set 6-0 in 22 minutes.
The second set began with Williams heading for the wrong side of the court.
The American, who has made late withdrawals from previous editions of the Zurich tournament, was whistled off the court following the umpire's announcement of her retirement "due to injury" at 3-0 down in the second set.
Williams later told a news conference she had strained a right thigh muscle just before starting her warm-up.
"I had a really good practice yesterday and was feeling really good," said Williams who had asked organisers to bring forward her match to Tuesday despite reaching Sunday's final at last week's Kremlin Cup.
NO QUITTER
"It was really out of the blue, just before the match. I thought Tuesday would be a perfect start for me and would give me a day off in between.
"I hate to quit, I'm not a quitter and when my trainer came out I said I don't want to quit. I don't like people to think 'she gave up'. But maybe I worry too much about what other people have to say."
Williams said she expected to be fully fit in time for the season-ending WTA Championships.
"They've told me I should be fine for Madrid," she said. "I just need to take a day off or two and then go back to work."
Schnyder's reward for Tuesday's light workout will be a second round encounter with the winner of Wednesday's final opening round match between Russia's Elena Dementieva and Italy's Francesca Schiavone.
"I don't think I've ever played a match like that but I just concentrated on playing my tennis," shrugged Schnyder in an on-court interview following Williams's departure.
"I was checking the situation and trying to focus on my own game. I still had to play some good shots and keep it together mentally which is not so easy."
Former world number one Amelie Mauresmo, booked her place in the second round with a scrappy 6-4, 4-6, 6-3 win over Greek qualifier Eleni Daniilidou.
The Frenchwoman looked in control during the opening set but then came off the worse in an error-strewn second set.
Apparently struggling with ankle problems for most of Tuesday's match, Daniilidou finally gave way with two consecutive dropped service games midway through the deciding set.
Mauresmo, seeded eighth in Zurich, will now face Ukrainian world number 25 Alona Bondarenko for a quarter-final place.
Ninth seed Marion Bartoli also struggled on Tuesday before overcoming China's Peng Shuai 6-7, 6-0, 6-1 to set up a second round meeting with Dutch wildcard Michaella Krajicek.
