Williams, 38, raced to a 5-2 within the opening set earlier than Sakkari drew stage however the American raised her recreation once more to take the early benefit within the rain-delayed contest.
Williams trailed 3-1 within the second set earlier than reeling off 4 video games in a row and was serving for the match when issues started to crumble.
World quantity 21 Sakkari dragged the set to a tie-breaker earlier than levelling the competition at 1-1, then surged to a 5-Zero lead within the decider and accomplished the upset win on her eighth match level with a robust forehand.
Sakkari stated she didn’t play properly however was delighted with the victory over the third seed.
“I knew it was going to be an unpleasant match from my aspect however I’m extraordinarily pleased with the consequence,” Sakkari stated.
“She’s a task mannequin for me and plenty of others. What she has achieved in our sport is exclusive and I do not know if anybody else goes to do it once more.”
Sakkari subsequent faces Briton Johanna Konta, who received previous Vera Zvonareva 6-Four 6-2.
Earlier, Naomi Osaka placed on a stable serving efficiency to beat Dayana Yastremska 6-Three 6-1 and advance to the quarter-finals the place she’s going to face Anett Kontaveit, who beat Marie Bouzkova 6-Three 6-3.
Osaka fired eight aces to zero for Yastremska and wanted simply over an hour to dispatch the 20-year-old Ukrainian.
“The serve is a very essential a part of my recreation and I simply must tune it up,” stated fourth seed Osaka, who was enjoying in simply her second WTA singles match for the reason that Tour resumed.
“The proportion nonetheless wasn’t that top at present so hopefully as I play extra matches it will get higher.”
Former world primary Victoria Azarenka improved her report in opposition to Alize Cornet to 7-Zero with a 6-Four 7-5 win to advance to the quarter-finals, the place the Belarusian will meet Ons Jabeur, who beat Christina McHale 6-Three 6-0.
The event, the ultimate tune-up earlier than the U.S. Open Grand Slam, is being performed at Flushing Meadows in New York as a substitute of Cincinnati as a result of COVID-19 pandemic.