Japan’s top-ranked player reeled off eight consecutive games at one stage to power into the quarter-finals.
It had all seemed to be going to plan for the American second seed Williams when she broke the 19-year-old Osaka in the fifth game of the opening set.
But then the Williams first serve deserted her when serving for the set at 5-4.
Today I accomplished one of my dreams ❤️❤️❤️
— NaomiOsaka大坂なおみ (@Naomi_Osaka_) October 11, 2017
Two double faults and a series of fierce ground strokes from Osaka which unerringly kissed the lines enabled the world number 64 to break twice and take the set 7-5.
“She played well,” a disappointed 37-year-old Williams told reporters. “You know I made a few errors at 5-4 and after that she played pretty flawless. I can only give her credit.”
Osaka, who had made headlines when she knocked Angelique Kerber out of the US Open in the first round last month, continued in the same vein at the start of the second set and raced into a 5-0 lead.
“I felt like I played offensively and hit really deep hard balls but she had the luck today and could return those balls even harder and deeper,” said Williams.
Williams briefly rallied to 5-2, but after a pep talk from Osaka’s coach, the Japanese refocused and closed out the match on her serve at the second time of asking after an hour and 24 minutes.
“Venus is someone I’ve respected and admired,” said Osaka, who had not been born when Williams reached her first Grand Slam final, at the 1997 US Open.
“I’ve grown up watching her. Even though she someone I admire, it’s just another opponent at the end of the day so I tried to focus hard.
Teenager topples No.2 seed Williams 7-5, 6-2! pic.twitter.com/TPfb3ZTAbX
— WTA (@WTA) October 11, 2017
“I feel like even if I hit one semi-short ball she would come in and crush it, so I had to play really well.”
Earlier, the seventh seed Daria Gavrilova battled into the quarter-finals with a 6-1, 2-6, 6-2 win over American Shelby Rogers.
Rogers and Gavrilova renewed their rivalry at Victoria Park after last month setting a record for the longest ever women’s singles match at the US Open with a three hours and 33 minute epic.
“I was really motivated,” said the world number 22 Gavrilova after avenging her Flushing Meadows defeat.
“She has such a great serve I knew I had to take my chances on her second serve.”
Rogers had come out on top 7-6, 4-6, 7-6 in their marathon New York encounter but on this occasion Gavrilova raced to win the first set 6-1 in just 26 minutes.
Rogers, ranked 55, hit back immediately to take the second 6-2 in a scrappy encounter littered with errors.
With both players coming under pressure on their serve in the final set it seemed a matter of who would crack first.
And at 2-2 and 0-30 it was Rogers who blinked, serving back-to-back double faults to hand the Russian-born Australian the crucial break.
Another followed and the Australian closed out the match in an hour and 44 minutes.
Unseeded Caroline Garcia of France won her second title in as many weeks as she stunned new world No. 1 Simona Halep in a closely-fought final of the China Open on Sunday.
Garcia is in the form of her life and edged out the Romanian second seed 6-4, 7-6 (3) to add the China Open to the Wuhan Open title she lifted last weekend, making it five WTA crowns in all.
Garcia’s feat was all the more remarkable because she was carrying a leg injury that has required frequent on-court treatment and completed a mammoth three-set quarter-final win well past midnight on Friday evening.
The 23-year-old, who is set to rise from number 15 to nine in the world, sank to her knees in relief when she finally sealed victory in the second-set tiebreak.
“I was like, ‘Seriously, this really happened?'” Garcia said of what thoughts came to mind after she won on her first match point.
“I mean, it was such an amazing two weeks. It went so fast. I have the feeling I started these tournaments yesterday or two days ago. To play every single day, it was just after every match you had to forget about what happened and be on the present again.
“Even this morning I couldn’t believe I was in the final. Like to win it on my first match point in the tiebreak against Simona, new No. 1, it’s very difficult for me to believe. Even I looked at my dad, and it didn’t help me to relax actually.
“It’s just amazing. It’s difficult to put words on what I’m feeling right now.”
With rain teeming down outside ahead of what turned out to be a cracker, a leak in the Diamond Court stadium roof had threatened to dampen proceedings.
But that was soon fixed and there was little between the two players until Garcia broke Halep in the 10th game to grab the first set.
The 26-year-old Halep had the superior mobility — Garcia had her right thigh strapped – but the French player was making the better shots.
One forehand winner was greeted with gasps from the mostly full arena in Beijing.
The second set was even more competitive and the attritional seventh game turned out to be a turning point.
Garcia was 0-40 down on her own serve until dragging it to 40-40 and then saving half a dozen break points before somehow winning the game to go 4-3 up.
The duo raced into the tie break, but Garcia now had the momentum and she held her nerve to make it a famous Wuhan-Beijing double.
Garcia is now on an 11-match winning streak that has included two top-five victories. She is in pole position to clinch the final qualification spot for the WTA Finals in Singapore.
Between her two sensational titles runs in China, her ascension to the world’s top-10, and her potential berth in Singapore, Garcia is spoilt for choice as to which feat is more special to her.
“It’s like if you ask me to choose between ice cream, chocolate cake. It’s like, I don’t know,” she said with a smile.
“It all means something. To win a title, it always means something because you finish the week undefeated. You stay forever a winner of this tournament. So it definitely means something.
“To be in the top-10 also means something because it’s a step in your career that you want to achieve. You never know if you’re going to reach it, but it’s a very important goal. It’s mean you are a part of the top-10 best player in the world.
“To have the chance to be in the fight for Singapore, it’s something after last year in doubles give you motivation to do it in singles because, for sure, means more.”
Britain’s Johanna Konta will have to at least reach the final in Moscow next week to stop Garcia from making the season finale in Singapore.
Despite her disappointment Halep will officially become world No. 1 for the first time when the latest rankings are out on Monday.
The Romanian paid full credit to her opponent for the win.
“I consider that she won the match, I didn’t lose it. Of course, I couldn’t be, like, 100 per cent after yesterday. It was a little bit tough. I felt tired a little bit. My legs were a little bit sore,” said Halep.
“But I think I fought till the end, which I’m really happy about. She played an amazing tennis. To win two tournaments in a row, it’s a great thing. She deserved to win today. She was better.”
Emotional Simona Halep called it the best day of her life as she surged to number one in the world for the first time after reaching the China Open final on Saturday.
The Romanian, who said her next goal was to win a maiden Grand Slam, defeated Latvia’s Jelena Ostapenko 6-2, 6-4 in their semi-final.
Her ousting of Spaniard Garbine Muguruza at the top of the women’s game will be officially confirmed on Monday when the latest rankings are released.
The 26-year-old Halep is the fifth woman to hold top spot this year, but the first Romanian in the history of the WTA.
She smiled broadly, then cried and was presented with a flower arrangement in the figure “1” — which she hugged tightly — to celebrate the landmark moment.
“My dream is true now, in that moment you cannot believe 100 percent that it’s happening, so I was in tears a little bit,” she said.
“Maybe first time on court (to cry) nice tears… It’s the best moment in my life and I want just to keep it.
“Now tomorrow already I have just to restart everything, to start again to play the same and to work harder.
“And I have a few more dreams in my career.”
We have a NEW World No.1…
— WTA (@WTA) October 7, 2017
Asked by AFP what those were, she smiled: “I tell you one, only one: to win a Grand Slam, which you know.”
Halep saw off former number one Maria Sharapova earlier this week in Beijing and Saturday’s defeat of Ostapenko had a whiff of revenge – the 20-year-old won their duel in the French Open final earlier this year.
Halep will face either Caroline Garcia of France or Petra Kvitova of the Czech Republic in Sunday’s China Open final.
She was always in control against the world number eight Ostapenko and put herself on the way to victory when she broke the talented Latvian in the first game of the first set.
Halep’s ascension to the top brings Muguruza’s four-week reign as number one to an end, while the others who held the honour in 2017 are Angelique Kerber, Serena Williams and Karolina Pliskova.
The outstanding Williams is temporarily out of tennis after having her first child.
In the lead-up to Beijing, Halep said she was unconcerned about becoming world number one, but admitted with a grin: “Of course I wanted it.
“When I was five points away I felt that I want it more and more.”