Katerina Siniakova took bragging rights in the latest edition of a rivalry dating back to her junior days, racing past Jelena Ostapenko 6-1, 6-3 in one hour and 14 minutes at the Omnium Banque Nationale.

The Czech first played Ostapenko 10 years ago, at a Grade 1 junior event in Berlin. Ostapenko won that match 6-1, 7-6(0) and led their combined junior and U16 head-to-head 3-2, but Siniakova has now won both of their pro meetings for the loss of just seven games across two matches.

Siniakova, fresh off capturing the doubles gold medal at the Tokyo Olympic Games alongside Barbora Krejcikova, benefited from a total of 38 unforced errors off her opponent's racquet. Ostapenko could only find 15 winners to counter her cascade of mistakes, which frequently came early in rallies, but Siniakova did a fine job of scampering around the court to elicit errors with her defence when called on to do so.

Ostapenko was also beset by six double faults in her first two service games, getting broken in the second. Though she committed no more double faults over the course of the match, she never quite found her radar on her groundstrokes.

There was the hint of a potential comeback when Ostapenko slammed a forehand winner to prevent Siniakova serving out the match, but a flurry of netted balls in the next game swiftly ended those hopes.

Later on Monday, Maria Sakkari became the first seed to move into the second round, as the No.11 seed from Greece advanced past Marie Bouzkova of Czech Republic, 6-4, 3-1, ret.

This is Sakkari's first trip to the second round in Canada after opening-round losses in 2018 and 2019. Currently ranked at a career-high World No.18, Sakkari had been 0-4 against Czechs this season before moving past the ailing Bouzkova.

Bouzkova, who had a breakthrough run to the Omnium Banque Nationale semifinals two years ago, claimed the first break of the match to lead 3-1, but that only started a run of four straight service breaks which returned the players to level footing through 4-4.

But Sakkari used strong returning to earn another break and serve for the set at 5-4, which she accomplished despite initially falling behind 0-30. Bouzkova, who took a medical time-out at 5-4 in the opener, fell behind 3-1 in the second set as well, then deemed herself unable to continue.

There was one upset of a seeded player early on Monday, as qualifier Oceane Dodin of France eliminated No.14 seed Karolina Muchova of Czech Republic, 6-3, 1-6, 6-2.

Dodin overcame 10 double faults to post her first win over a Top 25 player this season, winning 70 percent of her first-service points in the match. Muchova could only claim 58 percent of points behind her own first serve during the clash.

Three recent first-time Grand Slam quarterfinalists were also in early action on Monday. Paula Badosa, who made the last eight at Roland Garros, dispatched Wimbledon quarterfinalist Viktorija Golubic 6-2, 6-3. The Spaniard landed 72 percent of her first serves and tallied 23 winners to 20 unforced errors.

However, Ajla Tomljanovic, who made her Grand Slam quarterfinal debut at Wimbledon, was forced to retire after Fiona Ferro levelled their encounter at a set all, 2-6, 6-2.

American teenager Amanda Anisimova also advanced to the second round via retirement, as Tereza Martincova of the Czech Republic pulled out of their match with Anisimova leading 6-1, 4-3 in the battle between qualifiers.

Nadia Podoroska of Argentina, though, completed a straight-set win over Magda Linette of Poland on Centre Court, 6-1, 6-2. Podoroska never dropped serve in the match as she swept to victory in just under an hour.

Podoroska, the first Argentinian woman to play this tournament since 2011, had lost to Linette in their only prior clash, which came on the clay courts of Bogota in 2017.