OLYMPIA FIELDS, Ill. -- Even with a pair of silver trophies in his possession, Jon Rahm still couldn't believe what happened Sunday in the BMW Championship. And he saw only half of it.

Rahm was on the range on the other side of the Olympia Fields clubhouse, preparing for a playoff that no one really expected, when Dustin Johnson rolled in a 45-foot birdie putt down the ridge for birdie to force a playoff.

Moments later, Rahm faced a putt even longer and more difficult on the 18th -- a 66-footer that he had to send at nearly a 90-degree angle to the top of the ridge. From there, it was a replay of Johnson's putt as it headed down the slope, kissed off the pin and disappeared into the cup.

"I still can't believe what just happened," he said.

Neither could Johnson, going for his second consecutive victory. He could only laugh, at his putt and Rahm's winner.

"I played an unbelievable putt, got in the playoff and then Jon made an even more ridiculous putt on top of me," said Johnson, who at least kept his No. 1 ranking in the world and in the FedEx Cup.

The putts overshadowed a command performance by Rahm, who closed with a 66-64 weekend on an Olympia Fields course that played like the toughest test in golf. His only bogey on the weekend came on the fifth hole Saturday, when he spaced out and picked up his golf ball from the green without marking it.

There was the 6-iron from 218 yards for his third shot on the par-5 15th after his tee shot went into the trees and barely came out, setting up a key birdie. There was his 30-foot birdie putt on the par-3 16th for a two-shot lead that Johnson erased with two birdies of his own, none bigger than the final one.

"That stretch of waiting for DJ, him making the putt, going in the playoff, me making the putt, then trying to stay mentally in it just in case he made the last putt, it's been a roller coaster, but so much fun," Rahm said.

He put behind him the one-shot penalty that even on Saturday he worried would come back to haunt him, and he thought about it briefly when Johnson had the long birdie putt on the 18th in regulation.

All he could think about on the 18th green in the playoff was finding a way to get to the next hole, knowing he had a putt from one end of the green to the other and Johnson had a 30-footer.

And then it was over. Rahm won for the second time this year and for the 11th time worldwide in his four years as a pro. His first victory came at Torrey Pines when he made a 60-foot eagle putt and wound up winning by three.

"I think we all want the flashy finish, maybe not the stress that comes with it," Rahm said. "But I set out with myself to enjoy even the uncomfortable moments we had out there today. And man, it was fun."

The course that all weekend felt like a U.S. Open delivered the kind of excitement typical of the Masters.

Rahm tore through the back nine Sunday on his way to a 64, the lowest round of the tournament, to finish at 4-under 276.

Johnson, a 54-hole leader for his third straight tournament and coming off an 11-shot victory last weekend at TPC Boston, birdied three of his opening four holes to open a three-shot lead, dropped a pair of shots around the turn and then delivered in the clutch with his 45-foot birdie putt on the last hole for a 67.

Johnson goes into the Tour Championship as the No. 1 seed, meaning he will start the chase for the $15 million prize at East Lake in Atlanta at 10-under par, two ahead of Rahm, who moved up seven spots to the No. 2 seed.

Joaquin Niemann, a 21-year-old from Chile, also made a spirited run with a 67 and was in the lead until a bogey on the 14th and no birdies the rest of the way. He tied for third with Hideki Matsuyama, who had a 69. Tony Finau closed with a 65 to finish three behind. They were the only five players under par at Olympia Fields.

Mackenzie Hughes had reason to celebrate, too.

Needing a par on the 18th to move into the top 30 in the FedEx Cup, he put his approach into the front bunker, splashed out to 5 feet and raised both arms when the par putt dropped.

Niemann also moved into the top 30, though he was chasing victory all day.

Adam Long and Kevin Streelman were bumped out, and Long suffered the worst of those fates. He was projected 30th in the FedEx Cup until Corey Conners three-putted from 5 feet for double bogey on the final hole. That allowed Billy Horschel to move up enough spots on the leaderboard to move to the 30th and final spot by three points over Long.

Tiger Woods missed all the action. He made double bogey on his 17th hole in a round of 71, making this the first time he was over par in all four rounds of a tournament since the Bridgestone Invitational in 2010.

Woods failed to reach the Tour Championship for the second straight year. He now gets two weeks off before the U.S. Open at Winged Foot, and Olympia Fields proved to be a good test for that.