Edison (United States) (AFP) - Jordan Spieth's reign as world number one came to an abrupt end 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.