Russell, a 33-year-old who lives in Houston, converted five of his break point chances against the world number nine to triumph in 74 minutes.

It was Russell's first victory over a top-10 opponent in 13 attempts.

Russell booked his first tour-level quarterfinal of 2012. He'll face 19-year-old fellow American Ryan Harrison, a 6-2, 6-4 winner over Russian Igor Kunitsyn.

Second-seeded John Isner, playing his opening match after a first-round bye, rallied to beat Horacio Zeballos of Argentina 6-7 (3/7), 6-4, 6-2.

Isner arrived in Houston from Monte Carlo, where he led America to a Davis Cup triumph in France last weekend. He won both of his singles matches in the United States' 3-2 victory in the quarterfinals of the nations tournament.

On Thursday the 26-year-old didn't drop his serve and fired 16 aces in the match lasting two hours and 13 minutes.

Isner, ranked 10th in the world, is seeking a first career clay court title. He next faces defending champion Ryan Sweeting, A 6-3, 6-2 winner over fellow American Bobby Reynolds.

Fifth seed Kevin Anderson of South Africa defeated American Sam Querrey 7-6 (7/3), 3-6, 7-6 (7/2) to reach the quarterfinals.

Anderson, seeking to add a second title of 2012 to the one he captured at Delray Beach last month, next faces fourth-seeded Juan Monaco of Argentina. Monaco defeated Japan's Tatsuma Ito 6-3, 6-3.

Monaco, who claimed his fourth career title at Vina del Mar this year and was a semi-finalist at the Miami Masters, is through to his third quarterfinal of the year.

The other quarterfinal match-up was determined on Wednesday, with third-seeded Feliciano Lopez of Spain advancing to a clash with sixth-seeded Carlos Berlocq of Argentina.

In Barcelona, Sara Errani of Italy beat second-seeded Julia Goerges of Germany 6-2, 6-3 yesterday to reach the Barcelona Open semifinals.

The seventh-seeded Errani took advantage of Goerges' erratic serve to break five times on the outdoor clay. The Italian will face Carla Suarez Navarro, who beat Simona Halep of Romania 6-4, 6-1.

Suarez Navarro managed to break Halep eight times in nine service games and rallied from a 3-1 first-set deficit to become the only Spanish player to reach the semifinals.

Olga Govortsova of Belarus played Sorana Cirstea of Romania and Slovakia's Dominika Cibulkova faced Ukraine's Yuliya Beygelzimer in Friday's other quarterfinal matchups.

Former World No. 1 Jennifer Capriati, a three-time Grand Slam champion who also won Olympic gold in 1992 at Barcelona, has been elected to the International Tennis Hall of Fame.

Officials of the sports honor shrine announced yesterday that the former US teen star would be the final person to be inducted on July 14 during the ATP grasscourt event at Newport, Rhode Island.

Capriati will be joined by former World No. 1 Gustavo Kuerten of Brazil, Spanish legend Manuel Orantes, promoter Mike Davies and the late wheelchair tennis star Randy Snow.

All receieved at least 75 percent support from a selection panel.

"I'm thrilled. This is a dream come true and an extraordinary tribute," said Capriati. "Tennis has been my passion and dedication for my entire life and to be acknowledged for this passion and dedication is truly icing on the cake.

"I truly feel humbled to be a part of history and a.m. honored to be considered among the greatest of all time."