Resilient as ever, Rahm went out and created even some magic of his own.

From one end of the 18th green to the other, Rahm's putt from 66 feet rolled down the ridge and into the cup, setting off a roar so loud it nearly made up for not having spectators.

"Luckily it just looked really, really good on the way," Rahm said in a televised interview.

"I could hardly believe it."

The course that all week felt like a US Open delivered the kind of excitement typical of the Masters.

Rahm's big birdie putt on the first extra hole spared him thoughts of his blunder in the third round, when he picked up his ball on the fifth green without marking it, leading to a one-shot penalty and his only bogey of the weekend.

He tore through the back nine on Sunday on his way to a flawless six-under 64, the lowest round of the week, to finish at four-under 276.

Rahm celebrates after sinking his winning 66-foot putt. PHOTO: Andy Lyons/Getty Images.

Johnson, a 54-hole leader for his third straight tournament and coming off an 11-shot victory last week at the TPC Boston, delivered in the clutch with his 45-foot birdie putt on the last hole for a 67.

It was only good enough to stay at No.1 by a slim margin.

He also stays top of the FedExCup standings going to the Tour Championship, meaning he will start the chase for the US$15 million bonus at 10-under par, two stroked ahead of Rahm, the No.2 seed.

Australia will have two players at East Lakes GC after Adam Scott blew his hopes of joining March Leishman and Cameron Smith in Atlanta.

Starting Sunday in a share of third and playing alongside Rahm, Scott shot a 75 to slide down to 25th to leave him outside the season-long standings' top 30.

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Smith rounded out his week with a 69 to grab a share of 20th at five-over and play himself into some form, while Leishman's 73 on Sunday was his best round at Olympia Fields.

Jason Day's 68 was best of the four Australians in the final round but he, like fellow former World no.1 Scott, won't be at the PGA Tour's season finale.

Joaquin Niemann, the 21-year-old from Chile, made a spirited run with a 67 to be tied third with Hideki Matsuyama (69) and earn a spot in the Tour Championship.

Mackenzie Hughes had reason to celebrate, too, making a clutch five-foot putt on the 18th for a 71 that got him into the top 30.

Tiger Woods (71) failed to reach the Tour Championship for the second straight year.