Williams, making her first appearance on the WTA Tour since her defeat to Garbine Muguruza in the SW19 final, kept her nerve following a rain delay to close out a 6-1 3-6 6-3 success.
A 90-minute delay during the deciding set could not prevent Williams securing her first career win in Toronto.

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She said in her on-court interview: "This is my first win in Toronto dating back to 1995. I've had to wait more than 20 years to finally win a match here so it's really sweet."
The Rogers Cup alternates each year between Toronto and Montreal, the latter of which was host when Williams made her one run to the final in 2014.

Venus Williams of the United States celebrates after winning her match against Irina-Camelia Begu of Romania during Day 3 of the Rogers Cup at Aviva Centre on August 7, 2017 in Toronto, Canada

Image credit: Getty Images

French Open winner Jelena Ostapenko suffered a shock defeat to American qualifier Varvara Lepchenko.
Ostapenko won the first set 6-1 but lost the next two on tie-breaks as the 20-year-old lost in her first appearance since her quarter-final loss to Williams at Wimbledon.
Kristina Mladenovic was the other seed to lose in the first round on Monday. The 13th seed was beaten 6-2 6-3 by Barbora Strycova.

Venus Williams of the United States plays a shot against Irina-Camelia Begu of Romania during Day 3 of the Rogers Cup at Aviva Centre on August 7, 2017 in Toronto, Canada.

Image credit: Getty Images

Two-time grand slam winner Petra Kvitova is safely through to the second round after a 6-1 7-6 (7/5) win against Carla Suarez Navarro but f ormer US Open finalist Roberta Vinci suffered a straight-sets loss to Daria Kasatkina.
American Sloane Stephens overcame Yulia Putintseva 6-7 (4/7) 6-0 6-4 while Dominika Cibulkova was a straight-sets winner against Lesia Tsurenko.
Kirsten Flipkens and Naomi Osaka both progressed when their respective opponents, Ana Konjuh and Heather Watson, withdrew through injury when trailing by a set.
Fifteenth seed Anastasija Sevastova saw off Lauren Davis 6-1 4-6 6-3 to reach round two, where she will be joined by Lucie Safarova, Ekaterina Alexandrova, Daria Gavrilova, and Katerina Siniakova, who were Monday's other winners.
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