Diana Shnaider upset world number three Jessica Pegula 6-3, 6-3 on Saturday to reach the WTA Toronto Masters quarter-finals, where the 15th-seeded Russian will face Poland's Iga Swiatek.
The 22-year-old left-hander took only 73 minutes to dispatch Pegula and improve to 3-3 in WTA career matches against top-five rivals.
"I feel like this week I've been very comfortable on both defending and just firing some winners," Shnaider said.
"I feel like it was working well. I was choosing a bigger target today but sometimes ripping the ball."
Shnaider, a semi-finalist at this year's French Open, battled through breezy conditions in search of her sixth career WTA title and first since last August at Monterrey.
"The wind was so crazy," she said. "I feel like staying low in my legs and just trying to play deep... was very important."
Former world number one Swiatek, the seventh seed, rallied to defeat Ukraine's 10th-seeded Marta Kostyuk 3-6, 6-1, 6-2.
Swiatek, a four-time French Open champion who also won Grand Slam titles at the 2022 US Open and 2025 Wimbledon tournaments, snapped a seven-match losing streak in three-setters to top-20 opponents dating to last September.
Swiatek saved nine break points in the last two sets without dropping serve, saying she played "more brave" after losing the first set and knowing she "could play better" against Kostyuk.
"In the second I came out... playing a bit faster and more heavy and pushing Marta a little bit more," Swiatek said.
"I knew I can keep being solid while doing that. So then game by game I felt like it was a good plan and a good choice and I went for it."
Swiatek won her only match with Shnaider last year in three sets on Madrid clay.
World number one Aryna Sabalenka, the four-time Grand Slam winner from Belarus who will seek her third consecutive US Open title next month, plays a later fourth-round match against Russian 16th seed Ekaterina Alexandrova.
The victor will advance to a last-eight matchup against either American eighth seed Amanda Anisimova or Ukraine's ninth-seeded Elina Svitolina.
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