Third-seeded Elena Rybakina of Kazakhstan had to claw her back for a 6-7 (3), 7-6 (5), 6-3 two-day win over unseeded American Jennifer Brady — ranked 561 in the world — on Wednesday in Montreal.
Rybakina, who is ranked No. 4 in the world, earned her first career victory in Montreal.
Brady was leading 4-2 in the first-set tiebreak on Tuesday when the match was suspended by rain. Brady went on to win the set on Wednesday, but Rybakina bounced back and finished with 44 winners to win the last two sets and the match in 2 hours, 41 minutes.
Top-seeded Iga Swiatek of Poland and No. 4 seed Jessica Pegula of the United States cruised into the next round with straight-set victories. Swiatek bounced Czech Karolina Pliskova 7-6 (6), 6-2, and Pegula ousted Kazakh Yulia Putintseva 6-4, 6-4.
"Well, for sure it's nice to have some challenges and overcome them," Swiatek said about her win. "It wasn't an easy first round, but I'm happy that I stayed solid, and I could close it in the first set because after having — I played two weeks ago in Warsaw, but still, I changed continents."
Later in the night, No. 2 seed Aryna Sabalenka of Belarus dispatched Croatia's Petra Martic 6-3, 7-6 (5) in a match that finished one minute short of two hours, and seventh-seeded Petra Kvitova of the Czech Republic outlasted Italian Camila Giorgi 6-2, 5-7, 6-0 in the final match of the night.
But the night also brought the day's first two upsets, as No. 8 seed Maria Sakkari of Greece fell to unseeded American Danielle Collins 6-4, 6-2 in a match Collins dominated throughout. While Sakkari did break Collins four times, the 29-year-old American did the same a whopping seven times.
Also, 11th-seeded Brazilian Beatriz Haddad Maia fell to an unseeded foe, though that match was much more competitive. After losing her serve three times and losing the first 7-5 to Canada's Leylah Fernandez, Haddad Maia responded with a 7-5 win of her own. The two held serve for the first seven games of the final set before Fernandez broke Haddad Maia to take a 5-3 lead, then won the next game to take the set 6-3.
Earlier, sixth-seeded American Coco Gauff had no trouble with Great Britain's Katie Boulter, winning 6-2, 6-2 in 73 minutes, and No. 10 seed Daria Kasatkina advanced with a 6-2, 7-5 decision over fellow Russia Anna Blinkova.
Swiss 12th seed Belinda Bencic needed three sets to knock off the United States' Alycia Parks 6-3, 5-7, 6-4. No. 14 seed Karolina Muchova of the Czech Republic defeated Romanian Sorana Cirstea 7-5, 6-4. No. 15 seed Liudmila Samsonova of Russia was a straight-sets winner over China's Qinwen Zhang.
Ninth-seeded Czech Marketa Vondrousova beat Denmark's Caroline Wozniacki 6-2, 7-5.
—Field Level Media