Third seed Maria Sharapova is out of Wimbledon after losing 6-3 6-4 to world number 131 Michelle Larcher de Brito.
The 2004 champion fell three times on court number two and required lengthy treatment on her hip in the second set.
At one point Sharapova complained to the umpire that the court was dangerous but after the match she refused to use this as an excuse for her defeat.
"Those conditions are there for my opponent, I just took a lot more falls than she did," said Sharapova.
"I've seen a lot of players fall and take a few hits and a few injuries. So I think that's just part of the game, part of what we have to deal with.
"I don't think I've ever fallen three times in a match before in my career, so that was a little strange.
"But that's certainly not an excuse. I give her a lot of credit, she played extremely well today. She was really solid from the baseline.
"I don't feel like I was aggressive enough. I wasn't ready after the returns or the serves. She's someone that plays extremely aggressive. I just wasn't there."
Portugal's De Brito, 20, suggested the court was slippery because there was cut grass sitting on the surface.
"The dead grass hasn't been swept off so it's made it quite slippery," said the 20-year-old, who has reached the third round for the first time.
"I just tried to stay calm. I was playing so well. I was just trying to hang on in there and gave it my all and went for it."
Number 12 seed Ana Ivanovic is also out, losing 6-3 6-3 to 2012 junior champion Eugenie Bouchard.
The match was moved from an outside court to Centre after Victoria Azarenka pulled out through injury.
The 19-year-old world number 66 broke Ivanovic five times in a match lasting only 63 minutes.
"We found out (about playing on Centre Court) 15 minutes before going on," said Bouchard. "It was crazy and great to play before this crowd."
Ninth seed Caroline Wozniacki also suffered a surprise defest as she fell 6-2 6-2 to Czech Petra Cetkovska.
In what was only her third tournament since four months out with a stress fracture of her foot, world number 186 Cetkovska comfortably saw off the Dane in just 75 minutes.
Carla Suarez Navarro of Spain is Bouchard's next opponent before a potential fourth-round meeting with former champion Petra Kvitova.
Navarro, who is the 19th seed, recovered after losing the first set to beat Croatian Mirjana Lucic-Baroni 1-6 6-3 6-3.
Monica Puig, who knocked out fifth seed Sara Errani, is through to the third round after she beat Silvia Soler-Espinosa of Spain 6-2 5-7 6-4.
Kvitova advanced without hitting a ball after her opponent Yaroslava Shvedova pulled out with an arm injury.
The Kazakh became the seventh player to withdraw through injury on Wednesday.
Victoria Azarenka, the Belrussian second seed, was among the casualties, handing a walkover to Italy's Flavia Pennetta as she failed to recover from a knee injury sustained in her first-round win over Maria Joao Koehler.
Former world number one and 16th seed Jelena Jankovic is out, beaten 7-5 6-2 by Vesna Dolonc.
The Serb, who is ranked 97 in the world broke Jankovic five times on her way to setting up a third round clash with German Kirsten Flipkens.
American Sloane Stephens did make it through but she had to be at her best to see off the challenge of German Andrea Petkovic.
The 17th seed was on court for two hours and 36 minutes before eventually prevailing 7-6 (7-2) 2-6 8-6.
Marion Bartoli and Kirsten Flipkens overcame unseeded opponents with straight-sets wins over Christina McHale and Bojana Jovanovski respectively.