Swiatek was playing in her first tournament since winning her sixth Grand Slam title at Wimbledon last month
Wimbledon champion Iga Swiatek became the latest seed to fall at the Canadian Open as she suffered a surprise defeat by Clara Tauson in the fourth round.
Denmark's Tauson, ranked 19th, avenged her fourth-round loss to Swiatek at Wimbledon last month with a 7-6 (7-1) 6-3 victory over the second seed in Montreal.
Swiatek's exit comes after top seed Coco Gauff, two-time defending champion Jessica Pegula and fourth seed Mirra Andreeva were all knocked out.
"Obviously it's really great and it shows all the hard work I've been doing has been the right thing," said Tauson, who won her third WTA title in January - her first since 2021.
