Victor of the last two Grand Slams in US and Australia, the 21-year-old Japanese's bid for a third was lethargic in her first tournament as the world number one women's tennis player. The 23-year-old, who won her first career title in January in Hobart, prevailed in 1 hour 32 minutes for her biggest career success when Williams hit a groundstroke long. "I don't really like playing out points when I practise".
Madison Keys overcame Anna Blinkova 6-3 6-7 (5-7) 6-4 to advance to a clash with Siniakova, and teenager Iga Swiatek recovered from being bagelled in her first set to win 0-6 6-3 6-3 and set up a match with Halep.
Osaka, ranked world No. 1, lost 6-4, 6-2 at Roland Garros, ending a 16-match winning streak in Grand Slams.
Despite her loss here, and despite wins at the most recent USA and Australian Opens, this is the first time she was a top seeded player.
Williams has competed at five Grand Slams events since the birth of her daughter in September 2017 but has struggled for game time this year, playing only five tournaments so far. "I'm here again. I'm feeling good, and I have expectations for myself to play good tennis".
Defeating Serena Williams is a major accomplishment - especially at a major. Her first major tournament back was last year's French Open, where she withdrew before a fourth-round match because of a chest muscle injury.
Serena Williams of the US reacts after missing a shot against Sofia Kenin of the USA during their third round match of the French Open tennis tournament at the Roland Garros stadium in Paris on Saturday.
Williams had said she considered not entering the French Open at all.
"I didn't really care", Kenin said after her upset win, according to Eurosport's Tumaini Carayol.
But Kenin played quite well, never showing a trace of nerves.
Kenin's defeat of Williams came on a dramatic Saturday at Roland Garros that also saw world No.1 Naomi Osaka - the victor of the last two majors - depart.
"Before the match, I was really nervous", Halep said.
"Serena is such a tough opponent".
And then, her voice choking on her words, Kenin added: "Obviously, you can tell, with my emotions". Serbia's Djokovic meanwhile won easily 6-3, 6-3, 6-2 over Italian qualifier Salvatore Caruso.
So who is Sofia Kenin?
Williams's forehand was woeful and her opponent piled on the pressure to move 5-2 up with another break.
Keys and Barty have faced each other just twice, with each player earning a victory. And Kenin broke Williams four times, while only ceding one of her own service games despite Williams having six break point opportunities.
Alexander Zverev won his fifth five-set match at Roland Garros in just two years, seeing off Dusan Lajovic 6-4, 6-2, 4-6, 1-6, 6-2 to reach the fourth round.
"I want her to be ready", Mouratoglou said.
Still, Osaka said she is leaving Paris with a positive mindset.
Kenin performed brilliantly to reach the last 16 of a major for the first time in her career, meaning Wimbledon is Williams' next chance of getting the record-equalling piece of silverware.
Barty will be a warm favourite to progress to the semi-finals after dominating Keys 6-4 6-1 in Fed Cup in April - two years after losing to the American in the first round in Paris. I mean, that's always a massive achievement. "It was my best tennis".
Osaka's luck ran out in Paris as she committed 38 unforced errors in something of a blowout.
First win over a World No.1.
"I think that's probably what I've been doing best over the last 12 to 18 months. For me, this is something that I have wanted to do forever".
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