Johanna Konta, British number one came from behind to beat 11th seed Jelena Ostapenko in the first round of the Rogers Cup in Montreal.
Konta, ranked 43rd in the world after starting the year in ninth, prevailed 6-7 6-1 6-2.
She was pegged back from a 3-0 lead in the opening set and lost a tie-break 8-6 to the 2017 French Open champion.
But the unseeded 27-year-old dropped only three more games as she took the next two sets in 68 minutes.
Konta will face Belarusian Victoria Azarenka in the second round after the two-time Grand Slam winner beat France’s Kristina Mladenovic 6-0 6-1.
Also through is Maria Sharapova, who beat fellow Russian Daria Kasatkina in straight sets.
Wimbledon champion Angelique Kerber and Petra Kvitova, a two-time winner at the All England Club, have also taken their places in the last 32.