World No 1 Serena Williams spent most of the late evening match on Court Philippe Chatrier trailing, but flicked the switch just in time, to reel off the last six games of the match with a flurry of winners.
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The American needed all her fighting qualities to beat Victoria Azarenka 3-6, 6-4, 6-2 and reach the last 16 of the French Open on Saturday.
Her victory means the 33-year-old is the first woman in the professional era to win 50 matches at each of the four Grand Slams.
Serena, champion at Roland Garros in 2002 and 2013 said, "I don't understand that, because it's just weird to me, because I was thinking 'are you sure Martina (Navratilova) didn't do it or Chrissie Evert?'"