Cincinnati, OH -- (Sports Network) - Serena Williams continued her solid return to the WTA Tour by breezing past fellow American Amy Frazier, 6-2, 6-2, to reach the semifinals at the $175,000 Western & Southern Financial Group Women's Open.

Williams, who missed six months this year due to injuries to her knee, has yet to drop a set this week. The seven-time Grand Slam champion won in 51 minutes Friday and will take on 2004 runner-up Vera Zvonareva in the semifinals Saturday.

Rain put a damper on play for a time Friday night, but Williams, who had the last singles match on court, continued her amazing play despite coming into the tournament 139th in the WTA rankings.

Top seed and defending champion Patty Schnyder of Switzerland had a difficult time, but edged past ninth seed Sania Mirza of India, 7-6 (9-7), 7-5.

Fourth-seeded Slovenian Katarina Srebotnik charged into the final four with a 6-2, 6-1 pasting of sixth-seeded Frenchwoman Marion Bartoli at the Lindner Family Tennis Center, while unseeded Russian Zvonareva rolled along by drilling fifth-seeded Serbian Jelena Jankovic 6-1, 6-1.