Murray upset, Williams sisters advance in Cincy

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Andy Murray, from England, complains about a shot during a match against Jeremy Chardy, from France, at the Western & Southern Open tennis tournament, Thursday, Aug. 16, 2012, in Mason, Ohio. Chardy won 6-4, 6-4. (AP Photo/Al Behrman)

MASON, Ohio (AP) — Serena and Venus Williams reached the quarterfinals of the Western & Southern Open on a hot and breezy afternoon. Andy Murray couldn't cope with the conditions.

Murray's off-day produced the biggest upset at the tournament on Thursday. His two-set loss to France's Jeremy Chardy left him with little hard-court experience heading into the U.S. Open.

Serena Williams extended her winning streak to 19 matches. Later, sister Venus needed a long break between sets before pulling off a 6-3, 6-0 win over Italy's Sara Errani.

Top-ranked Roger Federer reached the quarterfinals with his second quick match in two days. Mardy Fish and Juan Martin del Potro also advanced.

In the women's bracket, top-seeded Agnieszka Radwanska needed three sets to reach the quarterfinals. Samantha Stosur and Angelique Kerber also won.