Maria Sharapova was upset by Carla Suarez Navarro in a match interrupted twice by rain Thursday at the Rogers Cup.
Suarez Navarro won 6-2, 4-6, 6-2 to reach the quarterfinals.
The 16th-ranked Spaniard returned from the second delay to break Sharapova's serve and then fought off a break point in the next game thanks to a lucky net cord. She broke again in the final game.
The 25-year-old Suarez Navarro won her first WTA tournament this year at the Portugal Open in May.
The fourth-seeded Sharapova had struggled to a three-set win in her opening match Wednesday against Garbine Muguruza.
Earlier, Caroline Wozniacki routed Shelby Rogers 6-1, 6-0 to extend her run of one-sided victories. Rogers had upset local favorite Eugenie Bouchard on Tuesday.