- Defending champion Victoria Azarenka was forced to withdraw on Tuesday from the women's event at the ATP-WTA Cincinnati Masters with a right knee injury.
Officials said the tenth seed will be replaced in the draw by German Mona Barthel who plays later against Barbora Zahlavova Strycova.
"After my last match in Montreal, I tried to recover as much as possible. I started to feel a little bit better and did everything I could, but it's just not enough time for me to feel good to play a full match," said Azarenka.
"I tried to practise, give it a rest and work with my team. It's just not enough time. I wanted to give it my best shot until the last moment and try to do the best job as possible.
"It's unfortunate but it's the best decision for me."