Bo Van Pelt chipped in for eagle at the par-five 17th hole for a 65 that pushed him past a crowd of eight players and into the first-round lead at The Barclays when Rory McIlroy played poorly.
The Northern Irishman, winner in his last three starts including the British Open and PGA Championship, shot a three over-par 74 and trailed Van Pelt by nine strokes.
Among the long queue tied for second at five-under 66 in the opening tournament of the four-event FedExCup playoffs were Jim Furyk, who stood third on the points list, his old Ryder Cup team mate Hunter Mahan and England's Paul Casey.
The 25-year-old McIlroy blamed his poor play on a lack of preparation and not on fatigue despite taking time to celebrate his blistering run and attending to added business commitments.
"I think it's more to do with just not putting the adequate time into my game over the past week for obvious reasons," he told reporters after his first over-par round in competition since the final round of the US Open in June.
"So I'm going to grab a bite to eat here and go to the range this afternoon and work on a few things and really catch up on some practice that I probably missed out on over the past week."