Serena Williams is looking to defend her title at the WTA Championships. (Matthew Stockman/Getty Images)
ISTANBUL -- When Serena Williams is serving at her best, no one stands a chance. Petra Kvitova experienced that the hard way today, when Williams 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.
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.
Since the U.S. Open, Kvitova has lost 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.
"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."
"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. She played well and I need to improve my serve, for sure, to compare [with] her."
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.
"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."
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.
"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."