London - Wimbledon's famed grass courts were at the centre of a safety storm on Wednesday after Victoria Azarenka, Steve Darcis, the conqueror of Rafael Nadal, and Marin Cilic were amongst five players forced out with injury.
World number two and Australian Open champion Azarenka withdrew just minutes before she was due on Centre Court to face Italian veteran Flavia Pennetta for a place in the third round.
A right knee injury, suffered in a fall during her first round win over Maria Joao Koehler of Portugal on Monday which left her in tears and requiring 10 minutes of treatment, put paid to her hopes after an MRI scan showed extensive bruising to the knee.
Her fall happened on Court One, the same arena where Darcis knocked out Nadal.
Darcis, the world number 135, also took a painful tumble, causing the right shoulder injury which forced him to withdraw.
"The court was not in a very good condition that day. My opponent fell twice; I fell badly; there were some other people who fell after," said Azarenka, a semi-finalist in the last two years.
"It would be great if the club or somebody who takes care of the court would examine or try to find an issue so that wouldn't happen.
"There is nothing I could have done to make that better. There is nothing I've done wrong that cost me to just withdraw from Wimbledon."
Darcis, the world number 135, admitted he was devastated after being forced to pull out.
The 29-year-old Belgian had been due to face Poland's Lukasz Kubot in the second round, but was unable to recover in time after sustaining the shoulder problem in his remarkable triumph against Nadal 48 hours earlier.
"I think when you beat a guy like Rafa in the first round, you want to show more, you want to play more matches. I was playing maybe the best tennis in my life here," he said.
"So not to go on the court today, it's the biggest disappointment I have had."
America's John Isner, famous for winning the longest match in history at Wimbledon in 2010, pulled out after just two games of his second round tie against France's Adrian Mannarino.
"I just went to serve, and it was as I landed on my left leg, like I have done 20 million times playing this game. I just felt this sharp pain," said 18th seeded Isner.
"It just grabbed really badly and I knew I was in serious trouble then. I knew at that point it was not likely I was going to be able to play."
Croatian 10th seed Cilic joined the list of Wimbledon's walking wounded when he withdrew with a left knee injury.
Cilic, the runner-up to Andy Murray at Queens last week, was due to face France's Kenny de Schepper for a last-32 place.
"It's a very black day," said Cilic.
Czech veteran Radek Stepanek was also struck down by injury.
At 6-2, 5-3 down to Poland's Jerzy Janowicz, the 24th seed, he quit with a left hamstring injury.
Later Wednesday, defending champion Roger Federer, Andy Murray and Maria Sharapova take centre stage.
Federer, bidding to become the first man to win the title eight times, tackles Ukraine's Sergiy Stakhovsky on Centre Court.
But he will have to play in new shoes after Wimbledon authorities banned him from wearing his orange-soled shoes he used in the first round after they were found to contravene the tournament's strict all-white dress code.
Murray, the US Open and Olympic champion, switches to Court One to play Lu Yen-Hsun, the Taiwan player who beat him at the 2008 Olympics.
Sharapova, the third seed and 2004 champion, takes on Portuguese qualifier Michelle Larcher de Brito out on Court Two.
Two former world number ones were knocked out.
Lleyton Hewitt was dumped out by German qualifier Dustin Brown, the dreadlocked former Jamaica player winning 6-4, 6-4, 6-7 (3/7), 6-2
Brown, 28, the world number 189, will be playing in his first Grand Slam third round match where he will face world number 11 Mannarino.
Former women's number one Ana Ivanovic was knocked out by Canada's Eugenie Bouchard, the reigning Wimbledon girls' champion.
The 12th seeded Serb, who made the semi-finals in 2007, was beaten 6-3, 6-3 by the 19-year-old.