Wimbledon's new head groundsman Neil Stubley tells Reuters that despite complaints from some players that the grass courts are slippery, he is pleased with how the courts are playing.

"We are still confident this morning coming in that we are still producing the best tennis courts in the world. We are 100 percent happy with the playing surface and it's no different to any other year," he said.

Seven players either retired or pulled out of the tournament on Wednesday, which was an Open Era Grand Slam record.

Caroline Wozniacki, who badly twisted her left ankle and lost to Petra Cetkovska,  said she felt a difference in the courts from last year to this year and said the grass was playing similar to that of the 2012 Olympic Games. Maria Sharapova, who fell three times in the second round, called Court 2 "dangerous" in the second set of her loss to Michelle Larcher de Brito.

"It's her opinion,” Stubley said. “Lleyton Hewitt played on the court an hour before and thought it was fine. We are fully confident that we have prepared them how they should be prepared every year. By day four, as far as I am concerned, they are wearing exactly how they should be.”

Serena Williams said that watching all the injuries on Wednesday made her cautious during her win over Caroline Garcia on Thursday.

“Well, seeing all the falls, seeing all the slips, I definitely was a lot more aware going out there today, a little more on my toes,” she said. “So for me it played okay. But I went in there with a mind frame of be careful and be ready.”