The stars won through at the WTA Rogers Cup as world number one Karolina Pliskova, Simona Halep, Angelique Kerber and Garbine Muguruza progressed to the third round.
Playing for the first time as the WTA's no.1, Pliskova eliminated Anastasia Pavlyuchenkova in straight sets in Toronto on Wednesday.
Defending champion and second seed Halep accounted for Magdalena Rybarikova.
Angelique Kerber - the German third seed - prevailed against Donna Vekic, while Wimbledon champion Muguruza defeated Kirsten Flipkens.
PLISKOVA BEGINS TENURE WITH WIN
New ranking but same result for Pliskova, who ousted Pavlyuchenkova 6-3 6-3.
In her first singles match since rising to the summit of women's tennis, Pliskova was a class above as she hit 16 winners and 12 unforced errors in her 70-minute victory.
Awaiting Pliskova in the next round is Japanese teenager Naomi Osaka, who upstaged 15th seed Anastasija Sevastova 6-3 6-4.
HALEP MAKES WINNING START IN TITLE DEFENCE
Aiming for back-to-back Rogers Cup trophies, Halep saw off Rybarikova 6-3 6-4.
Albeit in different cities as she looks to claim consecutive Rogers Cup titles for the first time in 17 years, the Romanian star closed out victory in one hour, 38 minutes.
Halep will next face Barbora Strycova.
KERBER ENDS VEKIC'S RUN
Kerber was tested in her 6-4 7-6 (8-6) win against qualifier Vekic midweek.
A semi-finalist in Montreal last year, Kerber - competing for the first time since Wimbledon where she was dethroned by Pliskova - was forced to a second-set tie-break as she eventually closed out the match.
Sloane Stephens awaits after the American stopped 14th seed Petra Kvitova 7-6 (7-4) 3-6 6-2.
MUGURUZA UP AND RUNNING
Qualifier Flipkens put up a fight but Muguruza claimed a 7-5 6-2 win.
Spanish fourth seed Muguruza won eight of the last 10 games in the match, having been pegged back to 5-5 in the opening set.
Muguruza claimed five breaks and struck 28 winners to set up a meeting with Ashleigh Barty in the last 16 following the Australian's 6-3 5-7 6-4 success against 16th seed Elena Vesnina.
VENUS MOVES INTO LAST 16
American ninth seed Venus Williams booked her spot in the next round thanks to a 7-5 7-5 triumph against Katerina Siniakova.
Agnieszka Radwanska - seeded 10th - routed Timea Babos 6-0 6-1, but fellow seeds Johanna Konta, Svetlana Kuznetsova and Dominika Cibulkova crashed out.