Rory McIlroy struggles in opening round of The Barclays

Rory McIlroy reacts after his third shot on the par-five 13th in New Jersey

Rory McIlroy was nine shots off the lead after a opening three-over 74 in The Barclays, the opening event of the PGA Tour's FedEx Cup play-offs.

Chasing his fourth straight win after the Open, Bridgestone Invitational and US PGA, the 25-year-old Northern Irishman was out in 40 in New Jersey.

The world number one improved his card with two birdies on the back nine.

England's Paul Casey is among a pack one shot behind leader Bo Van Pelt of the United States, who is on six under.

USA Ryder Cup stars Hunter Mahan and Jim Furyk are also on five under, while Scotland's Russell Knox shot a 67 to finish two shots off the pace.

Masters champion Bubba Watson, US Open and Open runner-up Rickie Fowler, England's Justin Rose and South Africa's Ernie Els are all on three under.

After starting his round at the 10th, McIlroy only managed to hit seven out of 14 fairways, although he did drive the ball better on his second nine.

McIlroy finished his round by holing a 30-foot birdie effort, which followed a dropped shot at the eighth after a missed green and pulled six-foot putt.

His round got off to a bad start as his double-bogey six at the 12th was followed by a further immediate dropped shot at the par-five 13th.

Another bogey at the 18th sent him to the turn in 40 with his first birdie of the day not coming until the fifth, his 14th hole.

Mcllroy, who appeared on late-night US television with Tiger Woods earlier this week - a couple of days after an appearance at Manchester United's Old Trafford - blamed his opening-round efforts on a lack of preparation.

"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 said.

"I guess taking a week off and sort of getting back into it this week, I probably just needed to give myself a little bit more time. But I wasn't going to do that. I was enjoying myself."

McIlroy led the FedEx Cup standings coming into the tournament, followed by Jimmy Walker, Watson, Matt Kuchar and Furyk.

In the battle for Europe's Ryder Cup spots, Northern Ireland's Graeme McDowell, currently occupying the last automatic berth, is on one under, along with another hopeful, Lee Westwood, who has competed at the last eight Ryder Cups.

England's Luke Donald, a place behind McDowell in the standings, is level par, while countryman Ian Poulter, lying in 12th spot, is on one over as is defending FedEx Cup champion Henrik Stenson.