Toronto - Top seed Rafael Nadal blew past patchy Frenchman Benoit Paire 6-2, 6-3 on Wednesday to begin his quest for a fourth Canadian trophy at the Toronto Masters.
The world number one Spaniard was untouchable as he schooled Paire for the fourth time without a loss, taking 74 minutes as he broke six times.
Nadal won the event in 2005, 2008 and 2013.
"I was not at my 100 percent today," Nadal said.
"It's true that I did good work here the last five days, but at the same time it's true that I didn't work very hard at home.
"So the first match is an important victory for me, for my confidence. It's important that I have another match tomorrow too. So just try to keep going.
"I played a solid match, in the second set I had some troubles, but my return worked well. It was more about the mistakes from the baseline."
The 32-year-old will bid for the quarter-finals here for the first time since 2015 when he plays Stan Wawrinka, who staged another fightback in three sets, beating Marton Fucsovics 1-6, 7-6 (7/2), 7-6 (12/10).
Defending champion Alexander Zverev, seeded second and winner at the weekend in Washington, also advanced easily beating Bradley Klahn 6-4, 6-4.
Former top-ranked Novak Djokovic, a four-time champion, sent Canadian Peter Polansky to a 6-3, 6-4 defeat.
Two generations of local players split the difference with Milos Raonic, 27, heading out while teenaged gun Denis Shapovalov moved on.
American Frances Tiafoe beat Raonic 7-6 (7/4), 4-6, 6-1 in a match hit by a weather interruption of more than two and a half hours.
Teenaged prodigy Shapovalov eliminated Italian 14th seed Fabio Fognini winner last weekend in Los Cabos, 6-3, 7-5.
Djokovic expressed support for the new 25-second shot clock innovation designed to cut down on time wasting between points.
"I'm pretty comfortable with it - it's good to have shot clock in the tournaments prior to the US Open."
The 13-time Grand Slam title winner has now won 21 of his last 24 matches after a rollercoaster start to 2018 which saw him go 6-6.
Djokovic, the winner of 30 career Masters titles, will next face rising Greek Stefanos Tsitsipas, who beat seventh seed Dominic Thiem 6-3, 7-6 (8/6).
It was the second straight opening defeat for the Austrian, who also last week at home in Kitzbuehel; he reportedly arrived carrying a virus.
Wimbledon semi-finalist John Isner defeated Pierre-Hugues Herbert of France 7-6 (7/3), 6-2.
South Africa's fourth-seed Kevin Anderson needed three sets to beat unseeded Russian Evgeny Donskoy 4-6, 6-2, 7-6 (7/0). Anderson will play Belarus qualifier Illya Ivashka in the third round.
Third seed Juan Martin del Potro was forced to withdraw prior to his opening match due to a left wrist injury.
Results from the ATP Toronto Masters tournament on Wednesday (x denotes seeding):
Novak Djokovic (SRB x9) bt Peter Polansky (CAN) 6-3, 6-4
Karen Khachanov (RUS) bt Pablo Carreno Busta (ESP x12) 6-4, 7-6 (7/3)
Robin Haase (NED) bt Mikhail Youzhny (RUS) 7-5, 6-2
Illya Ivashka (BLR) bt Ryan Harrison USA 7-6 (7/5), 6-4
Frances Tiafoe (USA) bt Milos Raonic (CAN) 7-6 (7/4), 4-6, 6-1
Denis Shapovalov (CAN) bt Fabio Fognini (ITA x14) 6-3, 7-5
John Isner (USA x8) bt Pierre-Hugues Herbert (FRA) 7-6 (7/3), 6-2
Stefanos Tsitsipas (GRE) bt Dominic Thiem (AUT x7) 6-3, 7-6 (8/6)
Rafael Nadal (ESP x1) bt Benoit Paire (FRA) 6-2, 6-3
Alexander Zverev (GER x2) def Bradley Klahn (USA) 6-4, 6-4
Kevin Anderson (RSA x4) bt Evgeny Donskoy (RUS) 4-6, 6-2, 7-6 (7/0)
Stan Wawrinka (SUI) bt 1-6, 7-6 (7/2), 7-6 (12/10)
Diego Schwartzman (ARG x11) bt Sam Querrey (USA) 6-4, 3-6, 6-1
Daniil Medvedev (RUS) bt Felix Auger-Aliassime (CAN) 3-6, 6-4, 7-6 (9/7)