Samantha Stosur has been sent out in the second round of the Cincinnati Masters after another loss to Serena Williams.

The Australian, who suffered a 6-0 6-2 defeat to Williams in less than an hour Montreal last week, proved a tougher opponent on Wednesday as she pushed the top seed to 7-6 (7) 7-6 (7).

In the men’s competition, Lleyton Hewitt and Marinko Matosevic also posted second-round losses.

Hewitt was beaten 6-1 6-4 by Italy’s Fabio Fognini, while American John Isner defeated Matosevic 6-3 7-6 (7/1).