|The Barclays second-round leaderboard|
|-7: B Watson (US); -6: J Dufner (US), H Stenson (Swe), T Finau (US), Z Johnson (US); -5: J Bohn (US), C Villegas (Col); Selected others: -3: Russell Knox (Sco); -1: P Mickelson; +1: L Donald (Eng), L Westwood (Eng); +2: J Rose (Eng), P Casey (Eng); +7: J Spieth (US)|
Jordan Spieth will lose his world number one ranking to Rory McIlroy after missing the cut at The Barclays in New Jersey on Friday.
Spieth was runner-up to Jason Day at the PGA Championship a fortnight ago to overtake McIlroy in the rankings after victories at the Masters and US Open.
The American, 22, followed his four-over-par first-round 74 with an 73 to finish five strokes over the cut.
The halfway leader is Bubba Watson, who carded a 68 after opening with a 65.
Spieth is the first player to miss the cut in his first start after becoming world number one.
His struggles mean McIlroy will return to the top of the rankings when they are published on Monday despite not lifting a club this weekend.
"I'm definitely searching for answers," said Spieth, who added it had been a "tough week".
|More from BBC Sport|
|Mo Farah chases record 5,000m title in Beijing||Jose Mourinho set for 100th home game|
|Watch GB 4x100m teams in relay action||England reach EuroHockey final|
"I don't know exactly what I'm going to do from here as far as how I get prepared for next week [the Deutsche Bank Championship] but I have some time to figure it out," he added.
"I've reached that peak already and I know it's going to be close enough to where if I just get the job done next week, I'll be back in that ranking.
"But again, that ranking, it's great once you reach it but it's not something that I'm going to live or die on each week. It doesn't really make much of a difference."
Behind leader Watson, Open champion Zach Johnson made five birdies as he carded a 65. The American sits one shot off the lead, alongside Henrik Stenson (66), Tony Finau (69) and Jason Dufner (68).