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.