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"&lt;p&gt;&lt;/p&gt;&lt;p&gt; Serena Williams is looking to defend her title at the WTA Championships. (Matthew Stockman/Getty Images)&lt;/p&gt;&lt;p&gt;&lt;/p&gt;&lt;p&gt;ISTANBUL -- When Serena Williams is serving at her best, no one stands a chance. Petra Kvitova experienced that the hard way today, when\u00A0Williams put on a serving masterclass to blast past Kvitova 6-2, 6-3 to remain undefeated in round robin play and become the first woman to advance to the semifinals at the WTA Championships.&lt;/p&gt;&lt;p&gt;Behind 11 aces and 27 winners to just 13 unforced errors, Williams took all the air out of the highly-anticipated match-up between two of the biggest hitters in the women's game, who also happen to be the last two winners of the WTA Championships.&lt;/p&gt;&lt;p&gt;Since the U.S. Open, Kvitova has \u00A0lost just one match, and said she was relishing the opportunity to pit her game against the best player in the world. Aside from a few too many forehand errors, the 23-year old Czech didn't play a bad match, hitting 17 winners to 19 unforced errors, a stable count given her low-margin game. But it seemed every time she earned a break point -- she earned four for the match -- Williams responded with an unreturnable serve.&lt;/p&gt;&lt;p&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Kvitova says she's looking forward to playing Serena&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;\"You know, when I play top players or a Grand Slam winner, such as Kvitova who has such a dangerous game, you've got to go in there knowing that anything can happen and I have to be really focused,\" Williams said. \"That was just what I did.\"&lt;/p&gt;&lt;p&gt;\"I think that she was really too good,\" Kvitova said. \"And she had a great serve today. I think it was the big difference between us two.\u00A0She played well and I need to improve my serve, for sure, to compare [with] her.\"&lt;/p&gt;&lt;p&gt;Kvitova served at a great rate, making 72 percent of her first serves, but she won just 57 percent of those points. Against Serena's return her lefty-serve was rendered innocuous.&lt;/p&gt;&lt;p&gt;\"From the baseline I think that we can play good rallies from both sides,\" Kvitova said. \"But the serve, she can hit almost 200 kilometers [per hour], so I don't think that my serve can be that fast.\"&lt;/p&gt;&lt;p&gt;The second semifinal spot out of the Red Group will be determined by a winner-take-all match between Kvitova and Angelique Kerber on Friday. When Kvitova won the tournament in 2011 she did so without dropping a match. As the only round-robin tournament on tour, the concept of still being in the tournament after suffering a loss is brand new for Kvitova.\n\"For me, [this is] the first time when I lost the match and I'm going to play tomorrow and still have a chance to go from the group,\" she said. \"So that's a little bit different, and for me it's a new experience again.\"&lt;/p&gt;"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.si.com/tennis/beyond-baseline/2013/10/24/serena-williams-semifinals-wta-championships>