ATLANTA -- Patrick Cantlay was on the verge of losing his two-shot lead on one hole, with nothing less than the FedEx Cup, the $15 million prize and his newfound reputation as "Patty Ice" on the line.

He was clutch as ever in his biggest moment Sunday in the Tour Championship.

Cantlay made a nervy 6-foot bogey putt on the 17th hole to stay one shot ahead of Jon Rahm going to the par-5 18th hole at East Lake. Then, he hit his longest drive of the week -- 361 yards down the middle -- with Rahm already in the fairway.

The final shot was a 6-iron from 218 yards to 12 feet -- the closest of anyone all day -- that all but clinched the one-shot victory, the FedEx Cup and perhaps even PGA Tour player of the year.

"It was the best shot I hit all week," Cantlay said.

Cantlay outlasted Bryson DeChambeau in a six-hole playoff at the BMW Championship. One week later, he held off the No. 1 player in the world with his one-shot victory over Rahm in the Tour Championship.

The nickname only surfaced last week, and it's starting to stick.

"To me, it just means cool under pressure, and I think that suits my personality really well," said Cantlay, who never changed his expression until a big smile when he tapped in for birdie and a 1-under 69, waving his cap to thousands of fans around the green.

It seems to suit his game, too.

Rahm couldn't get enough putts to fall. The U.S. Open champion stayed close all day, and his shot into the 18th was equally special. It landed right next to the hole on its second bounce, rolling through to light rough just off the green.

Cantlay expected him to chip in for eagle "because that's what he does." Rahm narrowly missed and shot 68, allowing Cantlay a safe two-putt for the win.

The victory was worth $15 million -- $14 million in cash, $1 million deferred -- for the 29-year-old Californian whose rise in golf was slowed by a back injury that kept him out for three years and nearly ended his career.

Now he has stamped himself among the elite in golf, boosted by the FedEx Cup postseason.

"It's fantastic," Cantlay said. "It's such a great honor because it's all year. I played really consistent all year and caught fire at the end. There's a lot of satisfaction considering all the work I'm put in my whole life."

Rahm, who started the tournament four shots behind and went into the final day two back, never caught Cantlay. He never let him breathe easy, either.

Cantlay took a two-shot lead with an approach to 6 feet for birdie on the 17th hole, and then nearly lost it all.

He drove to the right on the 17th, clipping a tree and dropping down into deep rough, and then hit a flyer over the green and the gallery. His pitch back to the green came up short and into more deep rough, and he had to make a 6-footer to save bogey and stay ahead.

That set up the final hole, where he could only match birdies with Cantlay.

"I gave it my all," Rahm said. "It wasn't enough."

Rahm was bogey-free over the last 28 holes, but he only cashed in on two birdies. He tied with Kevin Na for the low 72-hole score of the tournament at 14-under 266. They will split points toward the world ranking.

Cantlay started at 10-under par as the No. 1 seed and finished at 21 under.

"Patrick played great golf, and he was four shots ahead of me (at the start). And even though I might have been the better man over the week, he earned it," Rahm said. "That up-and-down after missing from 17, the second shot from 18 to almost make it is even more impressive.

"I think you can say he won this."

Rahm earned the $5 million consolation prize for finishing second in the FedEx Cup, while Na (67) picked up $4 million. Justin Thomas (70) birdied the last hole to finish fourth, which was worth $4 million.

"It felt really weird to have this feeling of disappointment of not winning on a day you are making $5 million," Rahm said.

Cantlay started the postseason by saying he did not like the format of the Tour Championship with the staggered start depending on a players' FedEx Cup position, and no official victory for the lowest score at the Tour Championship.

He's still not a fan, even if it worked out in his favor. All he could do was play the hand he was dealt, and he played his cards perfectly.

Even more satisfying was the manner in which he won the last two events -- the six-hole playoff against DeChambeau when he made one clutch putt after another, and delivering the key moment with the FedEx Cup on the line against Rahm.

"It's exactly why I play golf. I play golf so I can be in those moments against the best players in the world," he said. "It's why I practice so hard. It's why I'm in love with the game because it's that great vehicle for competition. It maybe makes it a little sweeter knowing that the guys I played against are the best players in the world."

Cantlay won for the fourth time this season -- no one else won more than twice. One of those victories was the Memorial, where Rahm had a six-shot lead after 54 holes and had to withdraw because of a positive COVID-19 test result.

That figures to make Cantlay a front-runner for PGA Tour player of the year, with Rahm (U.S. Open title, No. 1 ranking) and Collin Morikawa (British Open, World Golf Championship title), also likely to be on the ballot.

Rahm won the Vardon Trophy for the lowest adjusted scoring average.