In his first start since winning the U.S. Open, Dustin Johnson won another World Golf Championship on Sunday.

Johnson ran off three birdies on the back nine at Firestone and closed with a 4-under 66 to win the Bridgestone Invitational. He was helped in part by a surprising collapse by Jason Day.

Day, the world's No. 1 player, was tied for the lead when he hooked a 3-wood off the tee on the par-5 16th, hit across the fairway and tried to bend a shot around the pond. He went into the water, making double bogey.

Day did not hit a green in regulation over his last six holes.

Johnson now has three WGC titles, and goes to the British Open as the player to beat.