AP Sports Writer
MASON, Ohio (AP) - Serena and Venus Williams moved into the quarterfinals of the Western & Southern Open by handling the heat, humidity and wind. The conditions were too much for Andy Murray.
Murray's off-day turned into the tournament's biggest upset Thursday. He lost in two sets to France's Jeremy Chardy, leaving him with little hard-court experience heading into the U.S. Open.
Roger Federer, Mardy Fish and Juan Martin del Potro also reached the quarterfinals. Novak Djokovic advanced in the evening when Russia's Nikolay Davydenko had to quit after one set because of a sore shoulder.
On the women's side, Serena Williams won her 19th straight match, her last 12 in straight sets. Venus Williams also won in two sets. Top-seeded Agnieszka Radwanska needed three sets to reach the semifinals.