Serena Williams, the 10th seed, was beaten 6-2 7-5 by the 20-year-old and unsung Sofia Kenin. As a Moscow-born American, the 20-year-old Kenin idolises Maria Sharapova, and this result had faint echoes of Sharapova's famous victory in the 2004 Wimbledon final, even if Williams's aura has been diminished this season by her constant struggles with injury.
Down a set and a break, 3-2, against aggressive and seemingly fearless player-in-waiting Sofia Kenin, Williams looked disconsolate during the changeover.
Said her coach, Patrick Mouratoglou: "All I know is, she was not ready".
The world No 1 had won 16 consecutive slam matches, taking in titles at the 2018 US Open and 2019 Australian Open. "But once I got my feet used to the court, it was much better today".
"[If someone had told me I'd come this far] I would have thought they were lying, because I wouldn't expect to have gotten only to the third round", she said.
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Williams came from a set and a break down to beat Barty in the second round in Paris previous year but the Australian wasn't fussed about the rematch falling through. "Change the pace, do some drop shots, move Serena as much as she could, but the most important part of this was to believe she could win the match", said Kouyate, who also has traveled with Jo-Wilfried Tsonga on the men's tour.
I think she played really well. Her family moved to NY when she was a baby, and she now is based in Florida.
Barty won almost 80 percent of points on her fantastic first serve, and broke Petkovic four times out of six break points.
"If I had known what I would have to go through - thank God I didn't in the beginning", Alex Kenin said. I think I was overthinking this calendar Slam.
Despite giving her best, Serena lacked speed and the first strike that would give her the initial advantage in the rallies, counting to 30 winners and 34 unforced errors and playing some loose forehands in the pivotal moments for just one break from seven opportunities. She went 3-1 ahead in the second set before Williams, the 2002, 2013 and 2015 champion, clawed her way back to 3-3. And Kenin broke Williams four times, while only ceding one of her own service games despite Williams having six break point opportunities.
But Kenin played quite well, never showing a trace of nerves.