Top seed Rafael Nadal opened his Rogers Cup campaign with victory over Benoit Paire, while Novak Djokovic and defending champion Alexander Zverev also reached the round of 16.
Paire showed signs of life late but world number one Nadal advanced in straight sets at the ATP 1000 event in Toronto on Wednesday.
Wimbledon champion Djokovic was strong on serve as he ousted local wildcard Peter Polansky, while second seed Zverev was too good for Bradley Klahn.
Stan Wawrinka and Kevin Anderson survived but Dominic Thiem crashed out, along with Milos Raonic and Fabio Fognini.
NADAL A CLASS ABOVE
Seeking his fourth Rogers Cup, Nadal saw off fiery Frenchman Paire 6-2 6-3.
Nadal showed glimpses of his brilliant best as the 17-time grand slam winner responded to every challenge presented to him in a challenging second set.
Standing in the way of Nadal is Wawrinka after the three-time major champion outlasted Marton Fucsovics 1-6 7-6 (7-2) 7-6 (12-10).
DJOKOVIC ROLLS ON
It was a routine outing for ninth seed Djokovic as the Serbian star defeated Polansky 6-3 6-4.
The four-time champion needed just a solitary break in each set to advance to the third round in Canada.
Djokovic was expected to face Thiem but the seventh seed was upstaged 6-3 7-6 (8-6) by Stefanos Tsitsipas.
ZVEREV STAYS HOT
Citi Open champion Zverev continued his good form with a straightforward 6-4 6-4 win over Klahn.
Victorious in Washington, Germany's Zverev hit 16 winners and lost just 13 points in 10 service games as he won for the 42nd time this season.
RAONIC, FOGNINI SAY GOODBYE
Unseeded Canadian and former world number three Raonic was no match for Frances Tiafoe in a 7-6 (7-4) 4-6 6-1 loss.
There was some joy for Canada after emerging star Denis Shapovalov beat 14th seed Fognini 6-3 7-5.
Seeds John Isner and Diego Schwartzman moved on as Pablo Carreño Busta bowed out.