TORONTO: Qualifier Varvara Lepchenko rallied to stun French Open champion Jelena Ostapenko 1-6, 7-6 (7/2), 7-6 (7/5) on Monday in the first round of the WTA hardcourt tournament in Toronto.
American veteran Lepchenko, 31-years old and ranked 68th in the world, trailed 6-1, 3-0 before turning things around against the 12th-ranked Latvian, who had followed up her Roland Garros triumph by reaching the quarter-finals at Wimbledon.
"I think I woke up, I was a little bit in the sleeping mode for a set and a half," said Lepchenko, a former top-20 player herself. "All the credit to her, she played amazing tennis - she hardly missed any ball from the very beginning.
"Once I gave her a little push back, that's when the game started. I pretty much focused on my game.
"I know I have powerful shots and I'm as good a player as her, so I knew I just had to give my best, and it would be a battle."
Lepchenko notched her first win this season over a top-20 player and her first since she beat then 15th-ranked Timea Bacsinszky at the US Open last year.
The match was one of the Centre Court highlights on the opening day of this key US Open tuneup.
Seven-time Grand Slam champion Venus Williams, seeded ninth, headlined the night session, taking on Romanian qualifier Irina-Camelia Begu.
Two-time Wimbledon winner Petra Kvitova, seeded 14th fended off Spain's Carla Suarez Navarro 6-1, 7-6 (7/5).
Kvitova breezed through the opening set, but had to battle back from 1-4 down in the second to finish off the Spaniard in straight sets.
Top seed Karolina Pliskova and second-seeded Simona Halep -- who won the Canadian crown last year when the WTA played in Montreal -- were among the top eight players enjoying first-round byes.
In other early action on Monday, Czech Barbora Strycova upset 13th-seeded Kristina Mladenovic of France 6-2, 6-3.
Strycova, ranked 26th in the world, raced to a 5-0 lead in the first set as Mladenovic struggled to find her rhythm.
Although Strycova was broken the first time she served for the set, she finally served it out with a love game and quickly took a 4-0 lead in the second frame.
She again turned back a late challenge from Mladenovic, who cut the deficit to 4-3 but was unable to convert three break points that would have seen her level the set.
It was another disappointing Canadian outing for Mladenovic, who has never won a match in Montreal or Toronto.
Elsewhere, British qualifier Heather Watson bowed out early, retiring while trailing Japan's Naomi Osaka 6-1, 4-1 with a shoulder injury.
Belgium's Kirsten Flipkens was up 6-2 when Croatian opponent Ana Konjuh retired, the victory sending Flipkens into a second-round clash with fourth-seeded Wimbledon champion Garbine Muguruza of Spain.