The Latvian dominated the opening set of her match against qualifier Varvara Lepchenko of the United States, winning 6-1, to appear on course for a straightforward start to the tournament.

Lepchenko surprisingly turned the match around against her 20-year-old opponent, winning the next two sets on tie-breaks to complete a 1-6, 7-6, 7-6 victory.

France's Kristina Mladenovic was another surprise casualty in the first round as the 12th seed was beaten by the Czech Republic's Barbora Strycova 6-2, 6-3.

Venus Williams battled to a hard fought victory against Irina-Camelia Begu of Romania.

The 37-year-old American earned a 6-1, 3-6, 6-3 win to advance to the second round of competition.

While the majority of top seeds were awarded byes through the opening round, the Czech Republic’s Petra Kvitova was among the favourites who was in action.

She secured a convincing 6-1, 7-6 win over Spain's Carla Suarez Navarro.

In the men's competition, taking place in Montreal, Argentina's Juan Martin del Porto secured a 7-5, 7-5 win over American John Isner in one of the headline contests at the Uniprix Stadium.

France’s Adrian Mannarino eased past Russia’s Daniil Medvedev 6-3, 6-1 in his opening match.

His reward will be a second round encounter with Canada's home favourite Milos Raonic.

An all-Canadian clash saw Peter Polansky surprise Vasek Pospisil 7-5, 6-2 to reach the second round.

He will now face Switzerland's Roger Federer, with the number two seed set to celebrate his 36th birthday tomorrow.