MASON, Ohio (AP) -- Serena Williams is focused on her next match, not her distinguished history.
Williams took the first step toward winning a third consecutive tournament when she beat Lucie Hradecka of the Czech Republic 6-3, 7-6 (5) in the first round of the Western & Southern Open on Tuesday.
Williams, who last won three straight tournaments at the beginning of the 2008 season, has improved her world ranking from No. 175 to No. 31 in her comeback from injury and illness. She has won 12 straight matches, tying Kim Clijsters and Victoria Azarenka for the longest such streak on the WTA Tour this year.
"I'm not going for three,'' she said. "I just want to play the best that I can. I don't even think about that kind of stuff.''
Williams was pushed by Hradecka in the second set. She built a 5-1 lead before Hradecka rallied to take the lead. Williams regrouped to force a tiebreaker and advanced to the second round when Hradecka double-faulted on match point.
"I was upset that I didn't close it out,'' Williams said. "She started playing different and playing better - running a lot.''
Williams next plays Australian Samantha Stosur in the third round. Williams beat Stosur 6-4, 6-2 in the championship last week in Toronto.
Defending men's champion Roger Federer reached the third round with a 6-3, 7-5 win over Argentina's Juan Martin Del Potro, who had won the last two matches between the two, including the 2009 U.S. Open final.
"I expected a tougher match, for obvious reasons,'' he said. "It went better than I thought. I had a wonderful first set, and the second set, too. I was able to keep him from playing the game he likes to play. I was able to mix it up and serve well.''
French Open champion Li Na beat Lucie Safarova 6-3, 6-4 to become the first woman to reach the third round. The win was Li's first since losing in the second round at Wimbledon. She lost in the first round last week in Toronto.
"I needed some matches for the hard court,'' said Li, who reached the Australian Open finals in January. "It's always tough, but I was happy I could win the match today.''
Fourth-seeded Russian Maria Sharapova, sixth-seeded Czech Petra Kvitova and No 8 seed Marion Bartoli of France all cruised into the third round. Sharapova moved past Australian Anastasia Rodionova 6-1, 6-3, Kvitova advanced with a 7-6 (3), 6-3 victory over South African Chanelle Scheepers, and Bartoli posted a 6-1, 6-2 win over Ukrainian Alona Bondarenko.
Sharapova, runner-up this year at Wimbledon, felt as if she got her week off to a good start.
"I started the match quite well,'' she said."I had some ups and downs in the second set, but I played aggressively.''
Jelena Jankovic of Serbia, seeded 13th, advanced to the second round with a 6-0, 6-3 romp over Czech Iveta Benesova, but barely got to the court on time. Her car ran out of gas on the way to the match.
"I was like, 'Oh, my God. Great. I've got 20 minutes to my practice session,''' Jankovic said. "Luckily, the gas station was, like, two minutes walk. There were some players passing through and looking at us in the middle of the road like, 'What is she doing up there?' Pretty funny. It's not how you begin the day, but how you end it.''
Flavia Pennetta upset 12th-seeded Russian Anastasia Pavlyuchenkova 2-6, 6-3, 6-3, and 10th-seeded Stosur, 16th-seeded Shuai Peng of China and No. 17 seed Yanina Wickmayer of Belgium also advanced on the women's side.
In the men's first round, France's Michael Llodra upset 13th-seeded Mikhail Youzhny of Russia, 7-5, 3-6, 7-6 (4). Andrey Golubev of Kazakhstan eliminated No. 16 seed Stanislas Wawrinka of Switzerland 3-6, 6-4, 6-1 to end a losing streak of 18 consecutive matches in ATP play.
"It was very important,'' he said. "I lost a few matches when I was one or two points away from victory. It's really tough to digest.''
Eight-seeded Tomas Berdych of the Czech Republic became the first man to advance to the third round. Berdych defeated Argentina's Juan Monaco 7-6 (2), 6-0. Ninth-seeded Nicolas Almagro, 10th-seeded Gilles Simon of France and No. 15 seed Jo-Wilfried Tsonga, a Wimbledon semifinalist, also moved on.
In other key men's matches, Czech qualifier Radek Stepanek edged American John Isner 7-5, 5-7, 7-6 (4), and American James Blake moved into the third round with a 6-4, 6-2 win over Italian Fabio Fognini.