Maria Sharapova forced to withdraw from Birmingham

Sharapova, 31, reached the quarter-finals of the French Open before she was beaten in straight sets by Garbine Muguruza.

She had been due to play at Birmingham as part of her preparations for Wimbledon but she has withdrawn citing the need to rest her body.

“I have good memories of Birmingham so I’m disappointed not to be able to play this year." Sharapova said.

"I need to take care of my body and make sure I stay healthy and sometimes that means you have to take tough decisions like this one. I wish everyone in Birmingham a great tournament.”

Keys, 23, has pulled out with an abdominal injury.

“I am sorry to have to pull out of Birmingham this year." Keys said in her statement.

"Everyone knows how much I love playing on grass and I was looking forward to starting my grass season there, but unfortunately I aggravated an injury I sustained in Rome and need to rest as much as I can right now. I look forward to returning to Birmingham next year and playing in front of its great fans.”

Last year's Nottingham winner Donna Vekic has joined the tournament which also features Johanna Konta, Muguruza, Petra Kvitova, Elina Svitolina and Karolina Pliskova.

Nature Valley Classic Tournament Director Patrick Hughesman said: ”Adding Donna to the draw is a big bonus because she’s arguably one of the most dangerous players out there on a grass-court and I'm sure that she'll have good memories of reaching the final here in 2013.

"Of course it’s always disappointing to lose players of the stature of Madison and Maria but that's the nature of sport and we understand that their health has to come first, particularly after a gruelling clay court season. Fortunately our player list is still incredibly strong and this remains one of the best line-ups the tournament has ever had."