MADRID, Spain - A battle featuring former Top 3 Russians Nadia Petrova and Svetlana Kuznetsova, and Serena Williams continuing her title defense are among the second round storylines to keep an eye on at the Mutua Madrid Open.
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Tuesday, Second Round
 Nadia Petrova (RUS #11) vs. Svetlana Kuznetsova (RUS #40)
Head-to-head: Kuznetsova leads 5-2
Nadia Petrova and Svetlana Kuznetsova have played a big part in Russia being a huge part of the women's tennis scene during the 21st century. They have each won 13 WTA titles, including two Grand Slams for Kuznetsova. Also, Kuznetsova is a former World No.2, while Petrova has reached No.3.
Recent years have been kinder to Petrova, who has won four titles in the last two years and is one spot short of returning to the Top 10 for the first time in almost three years. Though Kuznetsova hasn't been triumphant since 2010, some solid results this year have her back in the Top 40 for the first time since August. And she cruised past Zheng Jie on Sunday for her first win in her five appearances in Madrid.
Petrova and Kuznetsova's history goes all the way back to the quarters of the 2004 US Open, where Kuznetsova eventually went on to her first major. While Kuznetsova has a comfortable lead in the series, four of the seven clashes have gone three sets - so another close one would be no surprise.
 Serena Williams (USA #1) vs. [WC] Lourdes Domínguez Lino (ESP #47)
Head-to-head: Williams leads 2-0
If there's a surface Serena Williams is vulnerable on, it would be red clay. She was victorious in Madrid last year when it was held on blue clay and defended her title last month in Charleston on green clay. Yet only two of her 49 WTA titles have come on red clay and none since the 2002 French Open. While she was pushed a bit in her opener here against Yulia Putintseva, she did get through in straight sets to raise her record on the year to 26-2 and continue her bid to keep Maria Sharapova from taking her World No.1 ranking.
Second round opponent Lourdes Domínguez Lino, the oldest player left in the draw at 32, is certainly comfortable on clay. Both of her WTA titles and her one runner-up showing, which came just two weeks ago in Marrakech, occurred on the dirt. Williams surrendered only eight games combined in her two prior match-ups with Domínguez Lino, but neither of those were on clay. Should she pull off the upset, it would be Domínguez Lino's first victory over a Top 10 foe.
[LL] Madison Keys (USA #62) vs. [WC] Anabel Medina Garrigues (ESP #63)
Head-to-head: First meeting
Prior to Madrid, Madison Keys had already shown several signs that she could be an American tennis superstar in the near future, like becoming the seventh-youngest player to win a WTA match as a 14-year-old at Ponte Vedra Beach in 2009, getting her first Top 20 win over No.17 Lucie Safarova en route to her first quarterfinal showing at Sydney earlier this year, reaching the third round of January's Australian Open and making another quarterfinal at Charleston last month. But perhaps the biggest hint at her potential was her securing her first Top 10 win over World No.5 Li Na in relatively easy fashion in the first round here on Sunday.
Another great challenge awaits the 18-year-old Keys in the form of a player 12 years her senior, clay court specialist Anabel Medina Garrigues. Her 10 clay courts titles are the most among active players and she will certainly have plenty of crowd support, being a native and resident of Spain.
Around the grounds?
Maria Sharapova and Christina McHale face off on Manolo Santana, as do Marion Bartoli and María-Teresa Torró-Flor, while Dominika Cibulkova and Sabine Lisicki clash on Stadium 3.