Wimbledon champion Iga Swiatek became the latest seed to fall at the WTA Canadian Open on Sunday, stunned 7-6 (7/1), 6-3 by 19th-ranked Dane Clara Tauson in the fourth round.
Swiatek, ranked third in the world and seeded second in Montreal, followed top-seeded Coco Gauff, third-seeded two-time defending champion Jessica Pegula and fourth-seeded Mirra Andreeva out the door.
Fifth-seeded American Amanada Anisimova followed later with a straight-sets loss to Elina Svitolina.
Tauson avenged a fourth-round loss to Swiatek at Wimbledon and called her second career victory over a top-five player "unreal".
"Obviously it's really great and it shows all the hard work I've been doing has been the right thing," Tauson said. "I'm getting more confidence in this kind of level and feeling like I belong here a bit more. I think that really helped me today in the important points."
Tauson booked a quarterfinal berth against Australian Open champion Madison Keys, who saved two match points on the way to a 4-6, 6-3, 7-5 victory over Czech Karolina Muchova.
It was the American's third match win of the year in which she overcame a match point.
Meanwhile, it was clear sailing for former world No 1 Naomi Osaka, who needed just 49 minutes to blast past Anastasija Sevastova 6-1, 6-0.
The second-quickest win of Osaka's career put her into her first quarterfinal at the 1000 or Grand Slam level since Doha in 2024.
Swiatek, playing her first tournament since winning her sixth Grand Slam title at the All England Club last month, looked out of sorts from the start on a breezy centre court.
She fell behind a quick break and failed to convert a pair of break chances in the eighth game as Tauson took a 5-3 lead in the first set.
The Polish star appeared to be finding her rhythm as she won the next three games to get her nose in front 6-5.
But Tauson, who won her third WTA title and her first since 2021 in New Zealand in January, held to force the tiebreaker and dominated, Swiatek surrendering the set with a double fault on the Dane's first set point.
Swiatek had saved a pair of break points in the eighth game of the second set when another untimely double fault gave Tauson the break and a 5-3 lead.
Tauson calmly served it out, claiming the victory when Swiatek belted a backhand into the net.
KEYS 'REALLY HAPPY'
Tauson will be up against a battle-tested opponent in Keys, who saved two match points on her own serve in the 10th game of the third set, striping a forehand on the first and escaping the second as Czech Muchova misfired on a service return.
"I'm really happy to get that win," Keys told the crowd. "After losing the first set and even being match point down, being able to figure it out – it's always a great day."
Osaka, who has struggled for consistency since returning from maternity leave in 2024, said the coaching shakeup she instigated this week – parting with Patrick Mouratoglou after less than a year and teaming up on a trial basis with former Swiatek coach Tomasz Wiktorowski – had energized her.
"I enjoy his coaching style. He's very direct and to the point. For someone like me, who my thoughts scatter around often, it's very helpful," said Osaka, who lost in the first round of the French Open and the third round at Wimbledon and arrived in Montreal ranked 49th in the world.
She will face Ukrainian veteran Svitolina, who beat Wimbledon runner-up Anisimova 6-4, 6-1.