(Reuters) - Venus Williams prevailed in a three-setter but French Open champion Jelena Ostapenko and 13th seed Kristina Mladenovic crashed out of Rogers Cup with first round defeats on Monday.
Williams outlasted a lengthy rain delay and pesky Romanian opponent Irina-Camelia Begu to win her opening match 6-1 3-6 6-3.
Less than a month after her run to the Wimbledon final, where she lost to Spain's Garbine Muguruza, 37-year-old Williams again had to turn back time against a young challenger.
After taking the opening set in dominant fashion, the American found herself in a fight as Begu rallied back to win a set before rain suspended action for more than an hour.
The decisive set was a rollercoaster with Williams moving ahead 3-1 only to lose consecutive games before bouncing back to seize three straight games and the match.
Earlier, Mladenovic was swept aside 6-2 6-3 by Czech Barbora Strycova while Ostapenko fell to American Varvara Lepchenko as upsets marked the start of the tournament.
Strycova's stunning triumph was followed by another surprise victory when 12th seed Ostapenko lost 1-6 7-6(2) 7-6(5) to American Lepchenko in two hours and 36 minutes.
After breezing through the first set, the 20-year-old Ostapenko's nerves began to show and unforced errors helped Lepchenko, 31, take the final two sets in tiebreaks.
Fan favorite Petra Kvitova, determined to improve following a knife injury to her hand inflicted by an intruder at home, beat Spaniard Carla Suarez Navarro 6-1 7-6(5).
The Czech’s six aces and 32 winners were too much for the 28-year-old Navarro, who had no aces and just seven winners.
"I'm feeling pretty tired right now," said Kvitova, who was trailing 4-1 in the second set before winning the tiebreak.
"I'm trying to come back as soon as possible but it is just a matter of time," added the 14th seed.
Strycova reached the second round for the fourth straight year, while Mladenovic remains winless in four attempts on the Canadian hardcourts after the first match on an overcast center court in Toronto lasted just 75 minutes.
"I started very well and felt good on court," said the 26th-ranked Strycova, whose only career title came in 2011 in Quebec City. "I was playing a lot of balls and being patient and I think that was the key in this match.
"In the second set she started to play a little bit better, she is a tough opponent. It is a great win for me."
Playing her first event since a first-round loss at Wimbledon, Strycova got off to blazing start by breaking the misfiring Mladenovic three times on her way to a 5-0 lead.
Japan's Naomi Osaka advanced 6-1 4-1 when Britain's Heather Watson retired injured while Russian Daria Kasatkina battled past Italy's Roberta Vinci 7-6(3) 7-6(1).
(Reporting by Steve Keating/Rory Carroll/Jahmal Corner; Editing by Larry King/Amlan Chakraborty)