After rain delays of six and 30 minutes, Nadal fought off two set points in the first-set tiebreaker. Play was stopped for 1 hour, 56 minutes with Nadal leading 2-0 in the second set.
“All the matches are difficult here,” Nadal said. “It was a tough first set. Then in the second, I was able to take advantage at the beginning, but then he broke me back.”
The 33-year-old Spanish star, a four-time Rogers Cup champion, will face Argentina's Guido Pella in the third round. Pella beat Moldova's Radu Albot 6-3, 2-6, 7-6 (2).
Second-seeded Dominic Thiem beat Canada's Denis Shapovalov 6-4, 3-6, 6-3. Thiem was coming off a victory on clay at the Generali Open in his native Austria.
Felix Auger-Aliassime won an all-Canadian match when Milos Raonic retired because of a back injury. Auger-Aliassime the first set 6-3, and Raonic won the second 6-3 before stopping play.
Poland's Hubert Hurkacz upset fourth-seeded Stefanos Tsitsipas of Greece 6-4, 3-6, 6-3, and France's Richard Gasquet beat fifth-seeded Kei Nishikori of Japan 6-7 (6), 6-2, 7-6 (4); and France's Adrian Mannarino, topped 11th-seeded Borna Coric of Croatia, 6-2, 6-1.
Sixth-seeded Karen Khachanov of Russia edged Stan Wawrinka of Switzerland 6-4, 6-7 (3), 6-2; eighth-seeded Daniil Medvedev of Russia topped Kyle Edmund of Britain 6-3, 6-0; and 10th-seeded Roberto Bautista Agut of Spain edged Diego Schwartzman of Argentina 6-2, 7-5; and
Cristian Garin of Chile knocked off 12th-seeded American John Isner 6-3, 6-4; and 14th-seeded Marin Cilic of Croatia topped Australia's John Millman 6-3, 6-4.