Unseeded Camila Giorgi rallied from a break point down in the final set to beat two-time defending champion Caroline Wozniacki 6-2, 2-6, 6-4 and advance to the Toray Pan Pacific Open quarterfinals on Thursday.
Trailing 2-0 in the final set, Giorgi broke back immediately and won six of the last eight games.
The Italian finished with 45 winners to the top-seeded Wozniacki’s 14.
It was Giorgi’s third win over Wozniacki, all on hard courts, but her first win over a top-10 players in four years.
Wozniacki, the world No. 2, found her game in the second set, saving all nine break points she faced — including one in the first game and five at 1-1 — to send the match the distance.
The Dane started the quicker of the two in the third set, winning eight of the first nine points to build a 2-0 lead but Giorgi fought back to set up a quarterfinal clash with wild card Victoria Azarenka.
“It was a good match, nice court, it was fun,” said the 37th-ranked Giorgi, who will hope for more of the same against Azarenka on Friday.
“I’ll just try to focus on my game plan as always and hope to play very consistently, like today.”
Azarenka beat seventh-seeded Ashleigh Barty 6-4, 6-2 for her first top-20 win since March.
Azarenka, who has tumbled down the rankings following a lengthy custody battle over baby Leo, will be the fresher of the two players.
Currently ranked 63rd and competing as a wildcard, she clinched the opening set with a thumping pass that was too hot for Barty.
Azarenka raced to a 4-1 lead in the second and closed out proceedings by jamming up Barty with a vicious kick serve into the ribcage on her second match point.
“That makes me feel a little old,” said the 29-year-old when informed she had reached the quarterfinals for the first time since 2012.
“I’m just trying to look day by day and see what happens.”
Czech Barbora Strycova won a tempestuous encounter with Estonian Anett Kontaveit 7-6, 3-6, 7-5 and next faces newly crowned U.S. Open champion Naomi Osaka.
Eighth seed Strycova took the first-set tiebreak 7-5 but both players screamed in frustration at their wastefulness in a contest that lasted well over three hours.
Having used all her challenges, Strycova huffily staged a sit-down protest after Kontaveit saved one of eight match points with a passing shot that replays showed missed the line by some margin.
But the Czech returned to her task and closed out the match when Kontaveit whiffed a drive-volley long.
Elsewhere, Croatian Donna Vekic beat Britain’s Johanna Konta 6-3, 7-5 to advance to the last eight, where she faces second seed Caroline Garcia of France.