Third seed Maria Sharapova is out of Wimbledon after she was beaten 6-3 6-4 by world number 131 Michelle Larcher de Brito.
The 2004 champion fell three times on court number two and required lengthy treatment in the second set on her hip.
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 her opponent five times in a match lasting just 63 minutes.
Sharapova, playing in her 11th consecutive Wimbledon, went out at the second round stage for the first time since 2009.
She struggled throughout the match and at one stage complained to the umpire that the surface was dangerous.
"It was unbelievable. It's probably the best win of my career," said De Brito.
"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. I saw Maria fall pretty hard and I know these grass courts can be a bit slippery and dangerous but she didn't give up.
"There's a lot of grass that has been cut and the dead grass hasn't been swept off so it's made it quite slippery - it is a tough surface to play on but it feels amazing to get into the third round and I will just try to keep going and do my best."
Ninth-seed Caroline Wozniacki was beaten 6-2 6-2 in her second-round match by Czech Petra Cetkovska.
In what was only her third tournament since returning from four months out with a stress fracture of her foot, world number 186 Cetkovska comfortably saw off her Danish opponent in just 75 minutes.
Ivanovic, who made the semi-finals in 2007, struggled to match her opponent, who is playing in just her second Grand Slam.
"We found out (about playing on Centre Court) 15 minutes before going on so I was really excited. It was crazy and great to play before this crowd," said Bouchard.
"I'm really happy to play well again here. Last year I won the juniors so it feels like my second home here."
The teenager will play Carla Suarez Navarro of Spain next 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.
The 19-year-old Puerto Rican is playing in her first Wimbledon and will have improved on her world ranking of 65.
She will now face Czech Eva Birnerova in the third round.
Kvitova made it through to the third round without hitting a ball after her opponent Yaroslava Shvedova pulled out with an arm injury.
She became the eighth player to withdraw through injury on Wednesday.