Dustin Johnson wins Northern Trust in a playoff over Jordan Spieth

The Northern Trust - Final Round

Andrew Redington

OLD WESTBURY, N.Y. — Coming into the FedEx Cup Playoffs, it felt like Dustin Johnson was flying a bit under the radar, if that's possible for the player ranked No. 1 in the world. Even entering the final round of The Northern Trust, down three strokes to Jordan Spieth, Johnson was lurking in the shadows, but seemed to be an after thought.

After five holes on Sunday at Glen Oaks, that deficit had grown to five, and it appeared as though Spieth would run away and leave everyone in the dust. Instead, Johnson plodded along, eventually carding a bogey-free four-under 66 to force a playoff, which he won on the first hole with a birdie for his fourth victory of the season.

Johnson, 33, had struggled since his unfortunate injury at the Masters, having looked in full control of his game after winning three consecutive events preceding the year's first major.

"It's been a tough road to get back where I feel like my game's able to compete out here again," Johnson said. "Finally, this week was the first week that I felt my game was back to where it was, where I feel like I got complete control over it."

The only sign he wasn't in control came on the final hole of regulation, where he was tied with Spieth at 13 under. Johnson's drive fanned into the right rough, leaving him no option but to lay up. His third shot landed 17 feet past, and after Spieth secured his par it became a must-make situation, something that has been rare for DJ in his career. A lack of experience made no difference as Johnson's putt caught the lip to force the playoff.

"A lot of my wins, I've had to two-putt on 18, or had an easy go at it," he said. "This was the first one I've really had to work at. It was good to make the putt, especially when I really needed one."

In the playoff, Johnson took an aggressive line, one he was hoping to take in regulation. This time it paid off and he piped one 341 yards down the fairway, putting him 60 yards ahead of Spieth's drive. After Spieth hit his just off the back of the green, Johnson knocked a wedge close, leading to the winning birdie putt.

With the victory, Johnson moves from fourth to first in the FedEx Cup standings.

At two under through five, Spieth looked like he'd run away with the trophy, but he put one in the water on the par-3 sixth, leading to a double bogey. Despite making another bogey on the ninth, and watching Johnson birdie the ninth and 10th to tie the lead, the three-time major champ still battled all the way to the finish and carded a one-under 69. It's just the second time in the last 11 tries he's failed to convert a 54-hole lead into a win.

Tying for third at nine-under 271 were Jon Rahm and Jhonattan Vegas. Spain's Rahm did his best to make it a three-horse race with Spieth and DJ, making three straight birdies at the 11th, 12th and 13th holes to get within a shot of the lead. But bogeys at the par-3 15th and 17th dropped him back to eight under. He did go out in style, rolling in a 24-footer for birdie at the 18th to finish T-3 or better for the fifth time on the PGA Tour this season.

Vegas posted one of the rounds of the day, a bogey-free five-under 65 that moved him from 29th to 10th in the FedEx Cup standings.

Paul Casey, who may have his playoff run sidetracked due to his wife's pregnancy, posted a final-round one-over 71 to finish in solo fifth at six-under 274. It's the Englishman's seventh top-10 finish of the season, and fourth inside the top-5.

Webb Simpson, Justin Thomas, Jason Day and Kevin Chappell tied for sixth at five-under 275.

Seven players tied for 10th at four-under 276, including Bubba Watson, who carded a final-round even-par 70. Watson's strong result moved him from 113th to 72nd in the standings, meaning he's advanced to at least the second leg of the FedEx Cup Playoffs in every season they've existed.

Also punching their ticket to Boston were Harold Varner III and David Lingmerth, who each entered the week outside the top 100. Varner III finished at two-under 278, good enough for a tie for 20th, moving him from 123rd to 91st. Lingmerth struggled on Sunday, posting a three-over 73, but still finished at even-par 280 in a tie for 29th, which helped him jump from 103rd to 87th.

A few notables saw their season end on Sunday, including Geoff Ogilvy (108th), Luke Donald (105th), Steve Stricker (115th) and Jimmy Walker (111th).