World No. 1 Serena Williams needed a two tiebreaks to emerge victorious over a nagging Samantha Stosur, 7(9)-6(7) 7(9)-6(7) at the Western and Southern Open on Wednesday.

The 17-time Grand Slam champion Williams survived a scare from Stosur having fought back from a 0-4 deficit in the first set tiebreak and 4-6 in the second set tie-break to claim an identical 7(9)-6(7) 7(9)-6(7) victory over the former U.S. Open champion.

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"It's good when you play a lot of close matches and you come out on top," Williams said. "I'm defeated, I'm down and I come back and win."

Williams will play Flavia Pennetta of Italy next in the battle of the 32-year-olds.

Meanwhile, Wimbledon champion Petra Kvitova bowed out early losing to Elina Svitolina in the second round of tournament. Svitolina won the biggest upset of the tournament as she ousted third seed Kvitova in just two sets 6-2, 7(7)-6(2),

The 19-year-old Svitolina broke the two-time Wimbledon champion twice in the first set. The second set was more of a challenge as the 24-year-old Kvitova went ahead 3-0, but Svitolina battled back and pushed the set into a tie-break.

Svitolina rallied for five straight points in the tiebreak to win her first career match against a Top 10 player.

The older Kvitova admitted of having more experience but conceded that there were also bad days such as her loss.

"Even if I'm older and have more experience, I can still have days like today," Kvitova said.

Kvitova seemed more comfortable in the grass courts of the All England Club in London where consistenly reached the quarterfinals for five straight years. She has won the prestigious tournament twice.

Wolrd No. 2 Li Na of China, who won the W&S Open title in 2012, was not able to compete in the event due to problems with her knee which she admitted of having since March.

Tagsserena williams, Elina Svitolina, li na, Samantha Stosur