(Reuters) – Dustin Johnson offered a reminder of why he is world number one when he beat Jordan Spieth in a playoff to win the Northern Trust in Old Westbury, New York on Sunday.

Johnson sank a three-foot birdie putt at the first extra hole to edge out Spieth after a compelling head-to-head final-round duel between the two Americans at the Glen Oaks Club.

Johnson forced the playoff by sinking a sharply-breaking downhill 17-foot par putt at the final regulation hole, his ball catching the right edge of the cup and toppling in at the par-four 18th.

He overcame a five-stroke deficit over the final 13 holes for his first win since he injured his back falling down stairs on the eve of the U.S. Masters in April.

After a quiet summer, Johnson stamped his authority with a closing 66 for 13-under-par 267 in the first of the PGA Tour’s four FedExCup playoff events.

Spieth shot 69 and the pair finished four shots clear of Jon Rahm and Jhonattan Vegas.

Johnson, who won three consecutive starts before hurting his back, joins Justin Thomas as a four-times winner on the PGA Tour this season.

He has 16 career victories.