PARIS (AFP) - Serena Williams battled back from a set down for the second straight match to defeat Victoria Azarenka 3-6, 6-4, 6-2 and reach the last 16 of the French Open on Saturday.
The 33-year-old American was staring defeat in the face at a set and 2-4 down in the second before finding her range in the nick of time.
She was also a break down early in the deciding set, but by that time she had found her range and she duly won six games in a row to clinch the win.
Williams will next play fellow American Sloane Stephens for a place in the quarter-finals as she continues in search of a 20th Grand Slam title.
Stephens made it through with a 6-4, 6-1 win over Tsvetlana Pironkova of Bulgaria, reaching the last 16 at Roland Garros for the fourth straight year.
"Today it was not easy, Victoria played very well and I was struggling," said the two-time champion Williams.
"She won the first set and I just said to myself 'allez, allez Serena, come-on.'" Azarenka was quickest out of the blocks in a late-starting match, taking the opening two games before Williams levelled at 2-2. Azarenka then won four of the next five games to take the set 6-3.
Williams was struggling with her usually mighty serve and she was broken again in the third game of the second set as Azarenka grew in confidence to take a 3-1 lead.
The American had a break point to get back level at 3-3 but three unforced errors in a row saw her 4-2 down instead.
Two games later she had another shot at taking the Azarenka serve and this time she made no mistake on her second break point with the Belarusian hitting long under pressure.
That proved to be the turning point of the match with Williams clearly in the ascendancy suddenly opening up with all the power she has at her disposal.
She levelled the set scores after a disputed line call that had the two players trading barbs and staring daggers at each other over the net.
Williams fell behind 0-2 at the start of the deciding set, but turned on the power as Azarenka wilted to win the last six games of the tie.
Williams and Stephens kept the American flag flying at Roland Garros after earlier defeats for Madison Keys and Irina Falconi.
Keys went down 6-4, 6-2 to Timea Bacsinszky of Switzerland, while Falconi fell 6-4, 6-1 to Julia Goerges of Germany.
In the same half of the draw Wimbledon champion Petra Kvitova, the fourth seed from the Czech Republic, finally found her form to outplay Romanian Irina-Camelia Begu 6-3, 6-2 in just 58 minutes, taking the last five games at a canter.
That was in stark contrast to her first two rounds that saw her grind out six sets and spend just four minutes short of five hours on the court.
"I think it was for sure the best match which I played here so far, so I'm really glad for it," Kvitova said.
Next up for Kvitova, who also won Wimbledon in 2011, but who has only managed a single semi-final in Paris in 2012, will be a fourth round tie against Bacsinszky.
Also through to the last 16 in early play was Italian Sara Errani, losing finalist in 2012, who gained revenge on Andrea Petkovic of Germany 6-3, 6-3.
Petkovic ousted Errani at Roland Garros last year at the quarter-final stage before losing in the semis.
There was disappointment though for another Italian, 2010 Roland Garros champion Francesca Schiavone, who lost 7-5, 6-4 to Andreea Mitu of Romania.
Ranked 100th in the world, Mitu is playing in her first French Open and her three wins in Paris this week were her first at Grand Slam level.
Her next opponent, with a quarter-final slot at stake will be 93rd-ranked Alison Van Uytvanck of Belgium, who ended the hopes of France's Kristina Mladenovic 6-4, 6-1.
Van Uytvanck was 1-5 in Grand Slam matches coming into Roland Garros, but like Mitu she has been able to benefit in her quarter of the draw from the first round defeat of sixth seed Eugenie Bouchard at the hands of Mladenovic.
"It's a big dream come true. I was happy enough winning in the first round and now being in the fourth round I can't believe it," said Van Uytvanck.