Edison -Jordan Spieth's reign as world number one came to an abrupt end on Friday after a missed cut at the Barclays ensured Rory McIlroy would return to top spot.
The Masters and US Open champion had toppled McIlroy from the number one ranking two weeks ago with a runner-up finish to Jason Day at the PGA Championship.
But in his first tournament since then, he endured two difficult days at Plainfield Country Club, where he followed up a first-round 74 with a 73 on Friday to miss the cut by five strokes with a seven-over total of 147.
Two-time Masters champion Bubba Watson was the halfway leader of the $8.25 million tournament, the first leg of the US PGA Tour playoffs.
Watson rolled in a 12-foot birdie putt at the 18th to cap a two-under 68 for a seven-under total of 133.
He separated himself from a quartet of players on 134 that included British Open champion Zach Johnson, who had five birdies without a bogey in a 65.
Johnson was joined at six-under by Sweden's Henrik Stenson (66) and Americans Tony Finau (69) and Jason Dufner (68).
But it was Spieth in the spotlight as the 22-year-old Texan tried to rebound from a first round that marked his worst score in relation to par all season.
He had confidently vowed to bounce back, but couldn't gain any traction as he followed a first-hole birdie with back-to-back bogeys at the fourth and fifth. Another birdie at the sixth was promptly followed by two more bogeys at the seventh and eighth.
Spieth rallied briefly with birdies at 10 and 11, but ended up with a double-bogey seven at the par-five 12th where he incurred a penalty for stepping on his ball while he was looking for it in a grassy hazard.
"Tough week," said Spieth, who was already certain to miss the cut when he capped his round with a bogey at 18.
As a result, McIlroy - who skipped this week's tournament - will return to number one in the world when the rankings are updated on Monday.
Spieth and McIlroy are both scheduled to tee it up next week at the Deutsche Bank Championship in Boston as the playoffs progress toward the season-ending Tour Championship in Atlanta, where a $10 million playoff bonus will be up for grabs.
"I don't know exactly what I'm going to do from here as far as how I get prepared for next week," Spieth said, welcoming the Friday start to next week's event. "I have some time to figure it out."
Spieth has fashioned one of the great seasons in golf with his first two major victories. He missed a playoff at the British Open by one stroke to finish with a share of fourth before his runner-up finish to Day in the final major of the year.
He has also won two other US PGA Tour titles, and hadn't missed a cut since the Players Championship in May -- one of just two prior missed cuts in 2015.
When he tees it up next week, Spieth said, he'll be thinking about winning the playoffs -- and letting the number one ranking take care of itself.
"That ranking, it's great once you reach it but it's not something that I'm going to live and die on each week," he said. "In my mind, it's just about trying to win the FedEx Cup at this point."
Spieth went into the Barclays atop the FedEx Cup standings, although Watson could overtake him with a win. With the Tour Championship counting the most toward grabbing the bonus, Spieth said he was far from out of it.
"Billy Horschel won the FedEx Cup after missing the cut in the first event last year and I'm in a better position to win the FedExCup than he was at the time," Spieth said. "So why can't I do it, you know?"