McIlroy overcame a three-shot deficit Monday in five holes, and then survived mistakes on the final two holes to close with a 4-under 67 and escape with a one-shot victory over Louis Oosthuizen.
McIlroy joined Tiger Woods as the only three-time winners on the PGA Tour this year, and with one of his wins being the PGA Championship, that might be enough for his peers to vote him player of the year. He also finally built a comfortable gap at No. 1 in the world.
Oosthuizen had a 12-foot birdie putt on the 18th hole to force a playoff, only it slid by on the right side for a 71.
Woods made an early charge to get back in the hunt, though he never got closer than three shots until a two-putt birdie on the par-5 18th gave him a 66. He finished in third place, two shots behind, and earned enough money to become the first player to surpass $100 million in PGA Tour earnings.
Phil Mickelson also had a 66 and tied for fourth, along with Dustin Johnson, who had a 70 and likely played his way onto the Ryder Cup team. Brandt Snedeker made a strong case for a captain's pick with a 65-67 weekend to finish sixth.
Davis Love III will announce his four picks Tuesday morning in New York.
McIlroy didn't make it easy on himself. The 23-year-old from Northern Ireland had a three-shot lead with six holes to play, and only a clutch bogey putt on the 17th hole kept him from losing all of his lead.
"I had a couple of wobbles coming in, but I obviously did enough and I'm very excited to get a victory," McIlroy said.
Oosthuizen, who had to cope with pain in his right shoulder earlier in the round, came back with two birdies on the back to get within one shot. McIlroy hit a chip over the 17th green into more rough, and it looked as if he would struggle to make bogey. Oosthuizen, however, missed the green from the fairway, chipped poorly to 10 feet and missed his par putt, and Boy Wonder calmly sank his 5-foot bogey putt to stay one shot ahead.
"The 17th hole cost me," Oosthuizen said.
McIlroy finished 20-under 264 and moved to No. 1 in the FedEx Cup, assuring he will have a shot at the $10 million bonus at the Tour Championship later this month.
It was the second time this year that Oosthuizen, who won the British Open by seven shots at St. Andrews two years ago, failed to win after leading going into the final round. McIlroy made an early charge with three straight birdies, but the turning point came on the fifth hole when Oosthuizen felt pain in his shoulder on a tee shot that sailed into the trees and led to double bogey.
The pain went away on the back, which the South African attributed to an adrenaline rush.
As always at the TPC Boston, this was quite a show on a late summer day in New England. This is the tournament that delivers duels between Woods and Vijay Singh (twice) and Woods and Mickelson. This time, all of them had fleeting hopes of winning.
McIlroy and Oosthuizen turned it into a two-man race, with Woods lurking until he couldn't convert enough putts. In the end, neither could Oosthuizen. He missed from just inside 10 feet for par on the 17th and from 12 feet on the 18th.
"I probably made all my putts yesterday," Oosthuizen said.
McIlroy becomes the youngest player with five PGA Tour wins since Woods, who had 15 wins at age 23.
There was other drama at the Deutsche Bank Championship, though it was not nearly as compelling as the top of the leaderboard.
Charley Hoffman went from the first page of the leaderboard to an unimaginable collapse until he steadied himself at the end. Hoffman, who was 13 under after a birdie on the eighth hole, played his next nine holes in 8-over par, including a quadruple-bogey 7 on the par-3 11th. He came to the 18th needing a par to finish among the top 70 in the FedEx Cup and advance to the third playoff event next week in Indianapolis.
He went over the green in two, barely chipped onto the putting surface, and then ran his putt 12 feet by the hole. He made the putt for par, and moves on.
"I didn't expect to be playing next week," Hoffman said. "Shooting 42 on the back nine, I don't think I deserved to play next week. But I guess I've got another chance."
Others who advanced included Dicky Pride, who birdied his last two holes to get the 70th spot by one stroke over Jonas Blixt; and Chris Kirk, who stumbled at the start only to birdie four of his last five holes.
Oosthuizen had a three-shot lead at the start of the final round, though he was never expecting an easy time. McIlroy rallied to cut a six-shot deficit in half on the back nine of the third round to give himself a chance, another example why he is No. 1 in the world.
Sure enough, McIlroy came out firing.
He hit a beautiful lag from just off the green on the par-5 second hole for birdie and rolled in a 12-foot birdie on the third to get within one shot. McIlroy hit 3-wood into the front bunker on the drivable par-4 fourth, the ideal position, and his bunker shot bounced off the pin to set up a third straight birdie. Oosthuizen stayed in front when his birdie putt from 25 feet dropped in on the final turn.
The fifth hole changed everything.
Oosthuizen reached for his shoulder after a horrific snap hook off the tee. The ball dove into the woods and landed in the middle of shoulder-high bushes, leaving him no option but to take a penalty drop out of the hazard. He laid up short of the creek and two-putted for double bogey. They were tied, because McIlroy's tee shot found a clump of native grass on the edge of a bunker, and he had to chip out short of the creek and made bogey.
Oosthuizen, though, was clearly hurting. He couldn't get through his swing on the next tee shot, which sailed into the bunker and kept him from attacking the pin. That's what McIlroy did, hitting 9-iron into 3 feet for birdie and his first lead. He never gave it back.
McIlroy and Oosthuizen could barely see Woods in his bright red shirt ahead of them, but they could hear what was going on. Woods ran off four birdies over the last six holes on the front nine, but he didn't make another one until the last hole.
"I certainly had my looks," Woods said. "I drove it really well on the back nine and just didn't hit it close enough at all. The only one I stuffed there was 17, and I missed that one."
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