Frenchmen Gael Monfils and Gilles Simon were among the first-round winners at the Rogers Cup on Monday.
Monfils, the 15th seed, was expected to be tested but he came out a comfortable 6-3 6-1 victor over Italian Fabio Fognini.
Fognini failed to convert any of his six break points in the first set and was troubled by a wrist injury that required treatment several times in Montreal.
The ninth-seeded Simon continued his dominance over Andreas Seppi, beating the Italian 6-2 6-4.
Simon made it five wins in as many meetings with Seppi, who was unable to break serve during the 82-minute clash.
The only other seed in action was another Frenchman, Jo-Wilfried Tsonga, and he led Croatian Borna Coric 2-1 before rain led to their encounter being suspended.
There were few big surprises at the ATP 1000 event played on hard courts in Canada.
Ivo Karlovic sent down 18 aces in a 6-4 7-6 (8-6) win over Pole Jerzy Janowicz, while Australian Bernard Tomic was untroubled by Joao Sousa in a 6-3 6-3 victory.
Thomaz Bellucci needed two hours, 42 minutes to edge past Pablo Cuevas 7-6 (7-4) 4-6 7-6 (7-4) and Tommy Robredo was tested before overcoming Feliciano Lopez 6-3 3-6 6-3 in an all-Spanish affair.
Americans Donald Young and Sam Querrey also advanced.
Querrey brushed past Martin Klizan 6-3 6-3 and Young was too good for Denis Kudla 6-3 6-4 in a meeting between two qualifiers.
Leonardo Mayer beat Chung Hyeon 6-3 6-4, Sergiy Stakhovsky got past local hope Filip Peliwo 6-1 5-7 6-2 and Gilles Muller claimed a 6-2 6-3 win over wildcard Philip Bester.