Putting the disappointments of the U.S. Open and PGA Championship behind him, Dustin Johnson closed with a steady two-under 69 Sunday to win the BMW Championship by one stroke.
Johnson finished his fourth PGA Tour victory at nine-under-par 275.
"It was a great day. To finally get it done, especially after all the things I've gone through this summer, to finally get it done on Sunday, it can't feel any better, especially since I played really good golf today," said Johnson, who earned $1.35 million for the win.
"I felt like I really stayed in the moment. I didn't get ahead of myself. I tried not to watch the leaderboard too much. I really did a good job of just being patient."
Paul Casey was five-under through 12 holes, but bogeyed three in a row from the 13th to fall out of the lead. The Englishman also shot 69 to finish one back at minus-eight.
Third-round leader Ryan Moore stumbled to a two-over 73 at Cog Hill to share third place with K.J.Choi (69), Kevin Na (70) and FedEx Cup points leader Matt Kuchar (72).
The featured pairing Sunday was world No. 1 Tiger Woods and No. 2 Phil Mickelson. Woods birdied three of four holes from the 14th to shoot one-under 70. That left him tied for 15th at minus-one.
Mickelson mixed six birdies and two bogeys in a round of four-under 67. He ended in a tie for eighth at four-under-par 280.
Johnson won the Pebble Beach Pro-Am for the second time earlier this year, and was one of the favorites heading into the U.S. Open at Pebble Beach. Johnson entered the final round with a three-stroke lead, but closed with an 82 to tumble into a share of eighth place.
At the PGA Championship, Johnson led by one on the 18th hole, but was penalized for grounding his club in a bunker on the final hole. The ensuing penalty dropped him out of the playoff which Martin Kaymer won.
"Pebble taught me a lot, I think. That's where I learned the most after getting off to a rough start, I kind of maybe got a little fast," Johnson said. "Everything starts moving fast in that situation. So I really learned to be patient and not rush things. I didn't rush any shot today. A few times I felt myself trying to rush a little bit, but I would stop, put my club back in the bag and come back and go through my routine and just take things slow."
Johnson trailed by one entering the final round Sunday, but poured in a 26- footer for birdie at the first to join Moore at minus-eight.
The 26-year-old Johnson stumbled to a bogey on the fifth to slip one back.
Casey collected his third birdie of the day at the eighth to take the lead at nine-under. Johnson bounced back with a birdie on the par-four eighth, where he converted a five-footer.
Around the turn, Casey looked like he was going to run away with the title. Back-to-back birdies from the 11th gave Casey a three-stroke lead. However, he faltered to three consecutive bogeys to tumble into a share of the lead with Johnson.
After his birdie on No. 8, Johnson cruised to eight straight pars. At the 17th, Johnson dropped his approach shot within two feet and tapped that in for birdie and a one-stroke lead.
Johnson found the short grass off the tee at the last, then knocked his second to 40 feet. He rolled his difficult birdie putt to a foot and after Moore finished out, Johnson kicked that in for par and the victory.
"On 17, I knew I needed to hit a good tee ball there because it was going to be my best chance of making a birdie, because 18 where the flag was, it's just a hard golf hole," Johnson explained. "I hit a really good drive, right where I was looking, and hit a great wedge shot in there."
Woods and Mickelson had very different rounds.
Woods, who won this title for the fifth time last year, had three bogeys through eight holes to slip to plus-three. He started to fight back with a birdie on the par-five ninth.
At the 14th, Woods kicked off a run of three birdies in a four-hole span that got him into red figures for the first time all week. He parred the last to finish at minus-one.
However, Woods failed to qualify for the Tour Championship for the first time since turning pro in 1996.
"I didn't play well early in the year and I didn't play well in the middle of the year," Woods stated. "Of late, I'm definitely getting along better, and am very pleased and looking forward to the future."
Woods failed to collect a victory this season, ending a run of 14 consecutive years with a win. He could continue that streak if he were to play in and win a Fall Series event. Woods is playing in the WGC-HSBC Champions tournament in Shanghai, but that is an unofficial event on the PGA Tour schedule.
Mickelson climbed to three-under with three birdies in his first seven holes. He tripped to a bogey on the eighth, but came back with birdies on 10 and 11. Mickelson faltered to another bogey at the 12th. He posted his final birdie on No. 15.
"He certainly brings the best out in me, and I enjoy being paired with him. I was looking forward to today's round playing with him, and we had a good time," Mickelson said of Woods.
Mickelson again failed to overtake Woods atop the world rankings, but with Woods out of the Tour Championship, Mickelson has another chance in two weeks.