There was a shock first-round casualty at the Coupe Banque Nationale as top seed Aryna Sabalenka was sent packing by Varvara Lepchenko on a day of upsets.
Sabalenka crashed out in her opening match, the in-form Belarusian a 6-4 7-6 (7-5) loser against Lepchenko in Quebec City on Tuesday.
Momentum was on Sabalenka's side heading into the WTA International tournament after winning her maiden title via the Connecticut Open in New Haven, while the 20-year-old also reached the Cincinnati Masters semi-finals.
But Sabalenka – who made it through to the US Open fourth round – was not good enough against her American opponent.
Sabalenka saved a pair of match points in the second set but it only delayed the inevitable as Lepchenko prevailed in one hour, 32 minutes.
Next up for Lepchenko is Marie Bouzkova, who beat Sesil Karatantcheva 6-2 6-1.
More seeds fell on Tuesday as Tatjana Maria and Lucie Safarova were eliminated.
Maria – the seventh seed – lost 6-2 6-2 to Rebecca Marino, while sixth seed Safarova was upstaged by Ons Jabeur 7-6 (7-4) 3-6 7-5.
Elsewhere, Jessica Pegula, Georgina Garcia-Perez, Olga Govortsova and Francoise Abanda advanced to the second round.