MASON, Ohio (AP) _ 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 quarter-finals 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 quarter-finals 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.
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 quarter-finals. 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.
