updated 10:10 p.m. ET July 20, 2006

MASON, Ohio - Serena Williams took another step in her comeback from a chronic left knee injury, beating Bethanie Mattek 6-3, 6-1 on Thursday to advance to the quarterfinals in the Western & Southern Financial Group Women’s Open.

Williams, playing in her first tournament since the Australian Open in January, will face Amy Frazier in the quarterfinals Friday.

“I’m just taking it one match at a time,” Williams said. “I didn’t expect super-spectacular results, but I didn’t expect bad results, either. I’m not looking too far ahead — one match, one match, one match.”

With Cincinnati Reds outfielder Ken Griffey Jr. and wife Melissa in the crowd, Williams committed 14 unforced errors to Mattek’s seven in the 37-minute first set, but had five aces to Mattek’s none.

The seven-time Grand Slam singles champion lost the first game of the second set to the 105th-ranked Mattek before taking the next six games. Williams won the last 10 points of the match, breaking Mattek at love in the final game.

“She just started hitting winners,” Mattek said. “She turned it up a little bit. I started missing shots a little bit and having a little trouble getting my serve in, and she took advantage of it.”

Williams said she didn’t play as well as she had in her first-round win over second-seeded Anastasia Myskina, but still felt she was improving.

“I feel fine,” Williams said. “I’m doing a lot of work off the court, and I hope it pays off, because I hate it. I feel like I can be faster—not just faster, but quicker.”

Earlier Thursday, fifth-seeded Jelena Jankovic of Serbia advanced by beating Italy’s Maria Elena Camerin 6-4, 6-4.

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The second set was interrupted by a rain delay that lasted almost 30 minutes.

“My legs started hurting a little bit,” Jankovic said. “I was glad I was able to finish it in two sets. At the end, I was saying to myself, ’I don’t need any unforced errors.’ I didn’t want to play three sets. I was starting to get tired.”

Jankovic will meet unseeded Vera Zvonareva of Russia in the quarterfinals. Zvonareva, who upset seventh-seeded Tatiana Golovin in the first round, advanced with a 6-0, 6-2 victory over Uzbekistan’s Varvara Lepchenko.

Sixth-seeded Marion Bartoli of France also advanced in the Tier III tournament, beating Russia’s Vasilisa Bardina 6-2, 2-6, 6-3. Bartoli will face fourth-seeded Katarina Srebotnik on Friday.

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