Top seed and defending champion Rafael Nadal dug deep to make a winning start at the Rogers Cup, while Greek star Stefanos Tsitsipas suffered a shock defeat in Montreal.
Nadal – a four-time winner of the ATP Masters 1000 tournament – shook off rust to overcome Dan Evans in straight sets on Wednesday.
The outcome was not as good for fourth seed and last year's runner-up Tsitsipas, who was stunned by Hubert Hurkacz.
Tsitsipas was not the only seed to fall, with Kei Nishikori, Borna Coric, John Isner and Milos Raonic also departing.
NADAL ON TRACK FOR RECORD-EXTENDING MASTERS TITLE
World number two Nadal survived to beat Brit Evans 7-6 (8-6) 6-4 en route to the round of 16.
Nadal trailed 5-2 in the first-set tie-break but won six of the final seven points to take control and eventually the match.
Contesting his first match since losing to Roger Federer in the Wimbledon semi-finals, Nadal claimed his 35th Rogers Cup victory and 378th Masters win – tying the Swiss superstar on the all-time leaderboard.
Nadal, who has won a record 34 Masters crowns, will face Guido Pella for a spot in the quarter-finals after the Argentinian beat Radu Albot 6-3 2-6 7-6 (7-2).
TSITSIPAS OUSTED, CANADIAN PAIR FOLLOW
This time last year Tsitsipas reached the final, however, the 2018 runner-up was a surprise casualty on Wednesday following a 6-4 3-6 6-3 loss to Hurkacz.
Hurkacz saved nine of 10 break points against the world number five, who failed to convert any of his four chances in the third set.
Canadian duo Denis Shapovalov and Raonic, meanwhile, were sent packing.
Shapovalov was beaten 6-4 3-6 6-3 by second seed Dominic Thiem and Raonic retired due to a back injury, with countryman Felix Auger-Aliassime benefiting after the match was even at 6-3 3-6.
Thiem will meet 14th seed Marin Cilic, while sixth seed Karen Khachanov awaits Auger-Aliassime after topping Stan Wawrinka.
MURRAY'S DOUBLES CAMPAIGN ENDS
Andy Murray and Feliciano Lopez said goodbye in Montreal, upstaged by Roland Garros finalists Jeremy Chardy and Fabrice Martin.
A five-match winning streak was ended following a 2-6 6-3 10-8 loss in the second round of the tournament.