Home favourite Aleksandra Wozniak overcame a second-set blip against Elena Vesnina before booking her place in the next round of the Bell Challenge in Quebec.
Fourth seed Wozniak wrapped up the first set without much fuss although Vesnina, who has dropped to 81st in the world rankings after being ranked as high as 22nd in 2009, hit back.
The Canadian held her nerve, however, and completed a 6-2 4-6 6-3 win over her Russian opponent to the delight of the Canadian crowd.
Czech sixth seed Barbora Zahlavova Strycova had to battle through a tough first set before eventually powering past Marie-Eve Pelletier 7-6 (7/2) 6-1.
Petra Martic and Lucie Hradecka, seeded seventh and eighth respectively, were also given stiff workouts.
Croatian Martic sealed a 6-4 7-5 win over lucky loser Jessica Pegula while Czech Hradecka claimed a 6-4 7-6 (7/5) victory over Maria Sanchez.
Wild card Eugenie Bouchard thrilled her home fans by coasting past the Grace Min 6-4 6-3.
Kristina Mladenovic and Lauren Davis, both of whom qualified for this tournament, advanced after seeing off Madison Brengle and Stephanie Dubois respectively.
There were also wins for Anna Tatishvili, Mirjana Lucic, Melanie Oudin and Petra Rampre.