Maria Sharapova fell three times during her straight-set loss to world number 131 Michelle Larcher De Brito and request medical attention.

Due to a knee injury she sustained in a first round clash, Victoria Azarenka pulled out before her match with Flavia Pennetta.

Richard Lewis, chief executive of the All England Club, said that the lawns were "as they should be" and rejected suggestions that the court surface was to blame for the injuries, and said that independently checked evidence suggested no different to the court surface last year.

"We have no reason to think this is the case. Indeed, many players have complimented us on the very good condition of the courts," he said in a statement.

"The court preparation has been to exactly the same meticulous standard as in previous years and it is well known that grass surfaces tend to be more lush at the start of an event.

The day was marked by the record-high number of withdrawals and the controversy over the courts.

Sharapova was seen mouthing what appeared to be the words "this court is dangerous" during the match, and said afterwards that she buckled her knee three times.

She described conditions on the court as "slippery" but refused to blame the lawn on Court Two for her defeat, saying conditions were the same for her opponent.

Azarenka said: "The court was not in a very good condition. My opponent fell twice; I fell badly; there were some other people who fell after."

Former world number one Caroline Wozniacki also slipped and played with tape on her right ankle as she lost to Petra Cetkovska in the second round.

Other players who pulled out were Steve Darcis, who defeated Rafael Nadal in the first round, Jo-Wilfried Tsonga, John Isner, Marin Cilic, Radek Stepanek and Yaroslava Shvedova.

The defeats of Federer and Nadal, and Tsonga's withdrawal leave Murray with a relatively open draw as the Scot seeks to end Britain's 77-year wait for a male champion at All England Club.