Rose bogeyed the 72nd hole of the event to fall back into that tie with Bradley, and the 2011 PGA Championship victor wasted no time in taking advantage of the situation.
Bradley won his fourth career title, his third in a playoff, to deny Rose his third triumph of the season even though the runner-up effort was enough to see the Englishman atop the rankings for the first time in his career.
Tiger Woods moved from 25th to 20th in the playoff standings with his sixth-place finish at the BMW. Because he didn't add to his schedule a tournament he had not played in the last four years, he is in violation of the PGA Tour's scheduling policy.
"I turned pro at 18 and it took me 20 odd years to get to world No 1, but my advice would be to just dedicate yourself to improving, to learning, to trying to get better".
The final round was pushed back from Sunday to Monday because of constant rain that led to poor course conditions.
Rose, unlike Bradley, will be among five players who can capture the US PGA $10 million season playoff crown by winning in two weeks at the season-ending Tour Championship in Atlanta.
"It's boyhood dreams", Rose added.More news: Watford hit back to stun Spurs and continue flawless start
"But obviously it's a big consolation being World No 1".
But bogeys on the 10th and 14th holes derailed his hopes and he ran out of holes, playing the back nine in 34. However, Schauffele was just one stroke behind after posting a 63 of his own, and four golfers were two shots back at 6-under, including Justin Thomas, the defending FedExCup champion.
They will try again on Monday but with a similarly dire forecast and a saturated course that simply can not take any more punishment, there is every chance the event will be reduced to 54 holes. However, he is still happy to get to the number one rank.
Such was the scoring at Aronimink that Woods had a 72-hole score of 263 for the sixth time of his career. "It was hard to get ready to play because I was like, 'Man, if they call it, I'm good.' But I was only three back".
Woods was referring to the special exemption that he was sure to get and unlikely to need in order to play in the championship he's won three times. Spieth started 27th in the FedEx Cup standings and took a step backward, finishing with a 73 to tie for 55th. That was about the time he was just starting to cope with back pain.
That means he will have played only 24 tournaments this season. Spieth is the first player to violate the policy, which began a year ago.
Northern Ireland's Rory McIlroy, who trailed then-leader Rose by one shot after round three, finished fifth following a 68.