American Piercy wins Canadian Open
Piercy closed with a three-under 67 to finish at 17-under 263 as he tied the oldest 72-hole scoring record on the PGA Tour.
Piercy two-putted from 50 feet for par on the 18th hole of the Hamilton Golf and Country club course to post his second career USPGA Tour victory.
McGirt was atop the leaderboard for much of the fourth round. But he three-putted for bogey on the 15th and failed to save par from a bunker on the final hole for a 69 that left him one shot adrift of Piercy.
Garrigus, the 54-hole leader, fired a 70 after he three-putted the 16th hole for bogey and finished in a tie for second.