Rory McIlroy got off to a disappointing start Thursday, shooting 3-over par 74 in the first round at the Barclays in Paramus, N.J.

The Northern Irishman, ranked first in the world and first in the FedExCup standings after winning the British Open, WGC-Bridgestone and PGA Championship in succession, trails the leading trio in the clubhouse by eight strokes.

Americans Cameron Tringale, Hunter Mahan and Charles Howell III, all shot 5-under rounds of 66 at Ridgewood Country Club to share the clubhouse lead.

McIlroy, starting on the back nine, made a double-bogey and two bogeys before the turn and a birdie on the par-4 fifth hole was canceled out by another bogey on his penultimate hole - the eighth.

"After you win the British and the PGA, I think it's going to be hard to get up mentally for any more golf," Phil Mickelson said. "That made the year right there. Anything after that is irrelevant I think and I think it's difficult for him to get up.

"Now he's such a good player, he'll end up coming back tomorrow and I would anticipate a low round. But there's nothing he can do that is going to equal what he's already done this year."

But McIlroy slightly limited the damage by finishing his round with a birdie on the ninth hole to end at 3 over.

Japan's Ryo Ishikawa and Scotland's Russell Knox were both a stroke behind the leaders after carding 67s.