Maria Sharapova and Venus Williams pull out of Cincinnati

Maria Sharapova and Venus Williams have pulled out of the Western and Southern Open in Cincinnati due to injury and illness respectively.

With the US Open due to start on August 31, second seed Sharapova decided not to risk worsening a leg injury.

The Russian, who has not played since the Wimbledon semi-finals, said: "It's a tough decision to make but I think it's the right decision to be ready for the US Open.

"It's not ideal preparation for New York, but that's the circumstance and I obviously want to give myself the best chance to be healthy there. That's the wisest move right now."

Williams was due to contest a potentially exciting second-round match against Ana Ivanovic but had to withdraw due to the viral illness which had troubled her since her opening-day victory.

On the court, rising star Belinda Bencic continued her superb run of form with a 7-5 6-3 victory over the 11th seed Angelique Kerber.

Bencic, who won the Rogers Cup in Toronto last week, fended off comebacks in each set from her German opponent.

Kerber came back from 5-1 down to make it 5-5 in set one and also hit back after trailing 3-1 in set two but was ultimately sunk by a huge 48 unforced errors and seven double faults.

Bencic will next face Italy's Flavia Pennetta, who beat Dominika Cibulkova of Slovakia 7-5 6-2 in the opening round.

America's Sloane Stephens comfortably defeated 10th seed Carla Suarez Navarro of Spain while former World No 1 Victoria Azarenka beat Lauren Davis by the same scoreline.

And Sara Errani and Agnieszka Radwanska were other seeds to crash out early on. Daria Gavrilova defeated Errani 6-1 4-6 6-2 while Anna Karolina Schmiedlova beat Radwanska 4-6 6-3 6-1.