New York: Two-time Wimbledon champion Petra Kvitova battled into the third round of the U.S. Open with a 7-6 (2), 6-3 win over Turkey's Cagla Buyukakcay on Wednesday.
In steamy conditions, the Czech, seeded 14th this year having dropped out of the top 10 for the first time in three years, escaped a first set tiebreak and then broke twice in the second for the victory on the Arthur Ashe Stadium court.
Kvitova, a quarterfinalist at Flushing Meadows last year, has often struggled with the humidity at the year's last Grand Slam and admitted it was anyone's guess how far she could go.
"You never know -- I never know," the 26-year-old said. "I was sick last week but am getting better every day and I feel good on the court and am feeling the ball well."
World No. 66 Buyukakcay, who became the first Turkish woman to win a WTA event in Istanbul earlier this year, achieved another first this week as she became the first woman from her country to appear in the main draw at the U.S. Open.
And the 26-year-old Buyukakcay battled Kvitova all the way, including in the first set when she came back from 5-2 down to force a tiebreak.
"She is a big fighter," Kvitova said of her opponent. "I knew that I had to play aggressive, I was tough in the tiebreak, especially when I was down 2-0."
"She's making history in Turkey and we're glad tennis is growing everywhere."
Kvitova now plays the number 22 seed, Elena Svitolina, after the Russian beat American Lauren Davis 6-1, 4-6, 6-3.
World No. 1 Novak Djokovic received a free pass into the third round when Jiri Vesely of the Czech Republic withdrew from their match due to a left forearm injury.
The walkover provided the top-seeded defending champion with an extended break to improve his niggling left wrist injury before his next match against either Guido Pella of Argentina or Mikhail Youzhny of Russia.
The 23-year-old Vesely, ranked 49th, beat Djokovic in the second round at the ATP Masters 1000 Monte Carlo event in April in their only meeting, making him one of two top 100 players with more wins than losses against the Serbian.
World No. 23 Ivo Karlovic is 2-1 head-to-head against Djokovic.
Seventh seed Roberta Vinci will not catch anyone by surprise with a run to the final like she did a year ago but the Italian continued to raise eyebrows with a speedy win over Christina McHale.
Vinci, who was unseeded last year when she lost in the final to compatriot Flavia Pennetta, has offered early signs that a return trip could be in the offing as she raced into the third round with a 6-1, 6-3 win over American McHale.
The straight-forward victory, which Vinci wrapped up in 63 minutes, followed a clinical first round win over Germany's Anna-Lena Friedsam that took 68 minutes.
Vinci, 33, will next face either Kazakhstan's Yulia Putintseva or Germany's Carina Witthoeft.