LOS ANGELES, July 30: Ernests Gulbis overpowered second-seeded Juan Martin del Potro to reach the semi-finals of the Los Angeles tournament on Friday, booking his first semi-final since January.

Gulbis, ranked 84th in the world, pounced early and never let up in a 6-2, 6-4 victory over the 2009 US Open champion.

Gulbis next faces his doubles partner, American Alex Bogomolov, who pulled off another upset with a 1-6, 6-4, 6-1 victory over fourth seed Brazilian Thomaz Bellucci.

Results (prefix number denotes seeding): Quarter-finals: Ernests Gulbis (Latvia) bt 2-Juan Martin Del Potro (Argentina) 6-2, 6-4; Alex Bogomolov Jr (US) bt 4-Thomaz Bellucci (Brazil) 1-6, 6-4, 6-1; 1-Mardy Fish (US) bt 8-Igor Kunitsyn (Russia) 6-2, 6-4; Ryan Harrison (US) bt Lu Yen-Hsun (Taiwan) 3-6, 6-3, 6-4.

SERENA DECIMATES SHARAPOVA

STANFORD (California): Serena Williams shrugged off her unseeded status and delivered a dominating 6-1, 6-3 victory over second seed Maria Sharapova to reach the semi-finals of the Stanford Classic tournament.

Williams, a 13-time Grand Slam champion who is unseeded thanks to a ranking slump caused by a lengthy injury layoff, showed Friday she's still a contender as she overpowered Sharapova, who struggled throughout with her serve.

Currently ranked 169th, Williams defeated Sharapova for the sixth straight time and improved to 7-2 overall against her.

Williams next faces big-hitting Sabine Lisicki, a 7-6, 2-6, 6-2 winner over fifth seed Agnieszka Radwanska.

Results: Quarter-finals: Serena Williams (US) bt 2-Maria Sharapova (Russia) 6-1, 6-3; 8-Dominika Cibulkova (Slovakia) bt Marina Erakovic (New Zealand) 6-1, 6-1; Sabine Lisicki (Germany) bt 5-Agnieszka Radwanska (Poland) 7-6 (7-4), 2-6, 6-2; 3-Marion Bartoli (France) bt Ayumi Morita (Japan) 6-1, 0-0 – Morita retired.

MARATHON GIRL PASZEK IN SEMIS

COLLEGE PARK (Maryland): Austria's Tamira Paszek is quickly becoming known for winning matches that drag on for a long time. And the never-say-die spirit that put her in a Wimbledon quarter-final last month lifted the third seed into a semi-final at the WTA hardcourt event on Friday after the second-longest women's match of the year.

Paszek, coming off her best Grand Slam showing, scored the last six points to outlast Canada's 117th-ranked Stephanie Dubois 5-7, 6-4, 7-6 in three hours, 42 minutes – one minute longer than her third-round Wimbledon victory.

Paszek's reward will be a semi-final against top seed Shahar Peer, who ousted eighth seed Alberta Brianti 6-1, 6-2 in only 66 minutes.

Results Quarter-finals: 2-Nadia Petrova (Russia) bt 5-Bojana Jovanovski (Serbia) 7-6 (7-4), 7-5; 3-Tamira Paszek (Austria) bt Stephanie Dubois (Canada) 5-7, 6-4 7-6 (7-2); Irina Falconi (US) bt Virginie Razzano (France) 6-4, 6-3; 1-Shahar Peer (Israel) bt 8-Alberta Brianti (Italy) 6-1, 6-2.—Agencies