MEMPHIS, Tenn. -- For a man who couldn't swing a golf club for six weeks, Dustin Johnson sure knows how to return to winning form quickly.
Johnson won the FedEx St. Jude Classic on Sunday in his second event after a back injury cost him nearly three months away from the PGA Tour, shooting a 4-under 66 that held off John Merrick by a stroke.
''Well, it feels really good, especially having so much time off,'' Johnson said.
Johnson pulled a muscle in his lower right back in early March lifting a jet ski at his home, and rest was the biggest part of his prescription for healing. He didn't return to the tour until last week at the Memorial, where he tied for 19th.
He began the final round two strokes back and held a piece of the lead three different times. He won his sixth career title with consecutive birdies on Nos. 16 and 17 and finished 9-under 271. Johnson said he didn't look at the leaderboard, trying to stay focused on himself.
''And you know, I did that,'' Johnson said. ''I had a lot of looks, lot of good looks and made a few putts coming down the stretch. Made great birdies at 16 and 17.''
Johnson, who picked up the check for over $1 million, led by only a stroke going to No. 18. Rory McIlroy, Chad Campbell and Nick O'Hern, three of the four who had a chance to tie Johnson with a birdie, knocked their tee shots into the lake. Johnson said he thought he might have been tied and made sure he hit the fairway to at least give himself a chance at birdie. Par was good enough.
Now Johnson is the first player since Tiger Woods (1996-2000) to win in each of his first five seasons on tour after leaving college, which he said means a lot. His six career wins are the most of any of the tour players in their 20s.
''It means I'm playing good golf, too,'' Johnson said. ''I come out every week and I try to just put myself in position to have a chance to win on Sunday.''
Johnson isn't concerned that no one has won on the PGA Tour and then won the U.S. Open the next week.
''I wasn't worried about the Open today,'' Johnson said with a smile. ''I was worried about winning the FedEx. Next is a whole different week.''
Merrick remains winless in 154 career tour starts. He shot a 69, recovering from a double bogey where he hit twice into water with a pair of birdies, and had a 272 total.
''The wheels were coming off the train. Hung in there and made a good putt for double,'' Merrick said. ''Hung in there, proud of myself.''
Davis Love III, the U.S. Ryder Cup captain, shot a 69 and tied for third with O'Hern (69), Campbell (68) and Ryan Palmer (66) at 273. McIlroy, who now heads to San Francisco and The Olympic Club to defend his U.S. Open title, had a 69 and tied three others at 274.
Tour officials pushed tee times up more than three hours and sent players off both tees in threesomes to avoid thunderstorms predicted for Sunday afternoon. With so many bunched closely together at the TPC Southwind course, that set up a rollercoaster final round with as many as eight players having a piece of the lead during the day.
Love, O'Hern and Merrick shared the lead overnight and had plenty of company before they teed off Sunday morning. McIlroy, Kevin Stadler and Campbell got quick birdies to join the group at 6 under, and Johnson made it a seven-way tie for the lead when he birdied his first hole.
McIlroy had a two-stroke lead all to himself after four birdies through 11 holes and appeared headed to the win. But he finished with two bogeys then his first double bogey in two trips to Memphis on No. 18 after hooking his 3-wood off the tee just a bit too much.
For a man who had missed three straight cuts coming to Memphis, McIlroy said he feels well prepared going into the U.S. Open after playing four straight rounds.
''Looking forward to getting to San Francisco, and I can take a lot from this week into next week,'' McIlroy said.
When O'Hern birdied Nos. 15 and 17, that set up a frenzied race to the finish with as many as four tied at 8 under in the final couple of holes.
Johnson carded four birdies and a bogey in the round. He took control with his consecutive birdies, rejoining the lead pack at 8 under when he rolled in an 11-footer on the par-5 16th. Johnson then moved to the top of the leaderboard by himself at 9 under by hitting his second shot from 161 yards to 9 feet on the par-4 No. 17 before sinking the birdie putt.
While Johnson waited, getting a play-by-play from analyst David Feherty, only O'Hern of Australia and Merrick had a chance to catch him, looking for their first career PGA Tour titles. O'Hern hit his drive into the water, while Merrick hit his near the cart path and finished with his own par to match the best finish of his career.
Divots: Johnson is the seventh player in his 20s to win on tour this year. ... This was the third time since 2005 that the winner of this event did not reach double digits under par. Jeff Maggert won at 9 under in 2006 and Justin Leonard won at 4 under in 2008.