Rory McIlroy, a two-time Canadian Open champion, had a challenging start to this year’s tournament.
McIlroy finished the first round with a one-over-par 71.
His round in Ontario featured three birdies offset by four bogeys, leaving him ten strokes behind clubhouse leader Thorbjorn Olesen.
Olesen’s impressive nine-under-par 61 included an eagle, eight birdies, and a single bogey.
McIlroy achieved a career Grand Slam in April with his Masters Tournament victory.
However, following a subpar performance at the US PGA Championship in May, his struggles continued into the Canadian Open as he prepares for the upcoming US Open.
Other notable performances included Irishman Shane Lowry’s promising six-under-par 64 and Scotland’s defending champion Robert MacIntyre and England’s Danny Willett, who finished one stroke behind Lowry.