Argentina's Emiliano Grillo shot a bogey-free 8-under 64 on Thursday to take the first-round lead in the Canadian Open.
The 22-year-old Grillo birdied three of the four par 5s at Glen Abbey. He won the Argentine Open last season for his biggest career victory, and lost in a playoff this year in the Puerto Rico Open.
Vaughan Taylor and Brian Harman were a stroke back. Two-time heart transplant recipient Erik Compton was at 66 along with Steve Wheatcroft, Tyrone Van Aswegen and Australian amateur Ryan Ruffels.
Jason Day, coming off a tie for fourth Monday in the British Open, opened with a 68.
Former Georgia Tech player Ollie Schniederjans had a 71 in his pro debut. He tied for 12th in the British Open.
South Africa's Tim Clark, the winner last year at Royal Montreal, shot a 72.