NEW HAVEN, Conn.(AP) American Sam Querrey has upset top-seeded Nikolay Davydenko 6-3, 3-6, 6-4 to advance to the semifinals of the Pilot Pen tennis tournament.

The hard-serving Querrey fired 15 aces, but was down in the pivotal ninth game of the third set Thursday. Four serves and two aces later, he took a 5-4 lead and then broke Davydenko at love to close out the match.

Davydenko needed a doctor to look at his right wrist midway through the match. He said it became sore from the force of Querrey's serves hitting his racket.

Elena Vesnina earned a spot in the women's semifinals earlier, defeating Anna Chakvetadze in straight sets, 6-1, 7-5.