Justin Rose admits his "boyhood dream" of becoming world number one was tainted by his agonising play-off defeat at the BMW Championship.
The Englishman climbed to the top of the rankings above American trio Dustin Johnson, Brooks Koepka and Justin Thomas after securing at least second place at the event in Philadelphia.
But his achievement was then slightly overshadowed following a disappointing additional hole at the Aronimink Golf Club which saw him edged out by winner Keegan Bradley.
"I know there is a bit of good news but it kind of takes a slight bit of the edge off," Rose told Sky Sports Golf.
Speaking about his new ranking, he added: "That's obviously boyhood dream stuff, something I'm incredibly proud of.
"I now have another string to the bow; if you're trying to sum up my career in three sentences - world number one would be right up there with the other achievements.
"I'm very proud of it, it's been a good stretch of golf, I've really played solidly for over a year.
"I always envisaged myself getting to world number one by winning tournaments and the last two weeks I haven't won.
"But delighted to have got to the top, absolutely."
Rose looked on course for the 10th PGA Tour title of his career after American Bradley bogeyed the 18th following a wild tee shot.
The 38-year-old narrowly missed a putt for par though, leaving the pair level on 20-under and forcing the additional hole.
Bradley, who fired a six-under 64 in the final round after beginning the day three shots behind Rose, had been watching anxiously at the side of the course with his family and he then returned to take advantage of his extra opportunity.
"The putt I hit to, I thought, win the tournament was probably as good a putt as I have ever hit to try and win a tournament and to see that spin out was unfortunate," added Rose, who carded a three-under 67 on his final round.
"Then we all saw the play-off, that was terrible, but it's one of those things.
"That's the thing with sudden-death play-offs, you make a mistake and it's all over."
After Sunday's wet weather postponed the final round, overnight leader Rose got off to a shaky start in defence of his one-shot advantage with a bogey on the first hole.
He quickly found his rhythm and five birdies, including successive ones on the 16th and 17th holes, put him in a strong position to take the crown, prior to his late wobble.
Americans Billy Horschel and Xander Schauffele finished tied for third, a shot off the pace, while Northern Ireland's Rory McIlroy was fifth on 18-under following a final round 68.
Tiger Woods, who celebrated his return to the United States Ryder Cup team by earning a share of the lead after the first round, was joint sixth alongside compatriot Webb Simpson on 17-under, while England's Tommy Fleetwood shared eighth place with Tony Finau, Rickie Fowler and Open champion Francesco Molinari.
Winner Bradley said: "It means everything, it took a lot of hard work to get back to this spot.
"It's just an incredible feeling right now. This has been a long time coming so I'm thrilled."
This win means so much. 🏆🙌@Keegan_Bradley is back in the winner's circle, winning the third #FedExCup Playoffs event @BMWChamps.— PGA TOUR (@PGATOUR) September 10, 2018
It's his first victory in 160 PGA TOUR starts.#LiveUnderPar pic.twitter.com/dBHitGZ2Qr