Ireland's major winners have work to do to make the cut in the RBC Heritage at Harbour Town Golf Links.

World No 1 Rory McIlroy struggled with a two-way miss, carding a one-over 72 left him eight shots behind leaders Ian Poulter and Mark Hubbard as Open champion Shane Lowry posted a three-over 74 and 2013 champion Graeme McDowell an untidy 75.

Pete Dye courses have often posed problems for the Holywood star McIlroy, who admitted he was frequently "uncomfortable" as he stood on the tee and found himself and consciously "steering" the ball through the trees with mixed results.

Visibly frustrated at times, he finished outside the top 100 in a slew of statistical categories from strokes gained from tee to green (107th), fairways hit (T123) to strokes gained around the green (119th) and strokes gained putting (103rd).

"I'm sort of missing my three-wood left and missing my driver right," McIlroy said, whose wedge play and putting was far from his best.

"I missed a few. I got a little better towards the end, hit some decent tee shots.

"If you're in any way like in two minds what to do off the tees around here and get a little bit sort of 'guidey', it can bite you. So I didn't get it in play enough to give myself shots or looks at hitting it close into greens and making birdies."

He added: "I wasn't particularly comfortable out there. I played here once before in '09, and I just can remember not being that comfortable around here then, and it's still sort of the same. 

"I'm just not comfortable and sort of trying to pick lines and really commit to shots. I just wasn't as committed today as I need to be around here.

Hoping to become more comfortable as he gets to know the course again, he said: "It's a course that, once you do get it in play, you can give yourself plenty of chances.”

Poulter (44) made seven birdies in a bogey-free 64 to end the day tied for the lead with Denver-born Hubbard (31), who had an eagle and five birdies on an equally immaculate card.

They lead by one stroke from a seven-strong pack that includes Norway's Viktor Hovland, Colombian Sebastian Muñoz, Michael Thompson, Webb Simpson, South African Dylan Frittelli, Brice Garnett and Ryan Palmer.

The resurgent Jordan Spieth (26) is lurking just two shots off the lead after recovering from a triple-bogey seven at the 418-yard 12th (his third) where he drove out of bounds and thee putted.

The Texan birdied the 13th (his fourth), then covered his homeward nine in seven-under 29 by following a run of six birdies in a row from the second with a closing birdie at the ninth.

"Today wasn't really a roller coaster," Spieth said. "That triple, again, it was a bogey at worst if it doesn't ricochet 25 yards out of bounds. 

"Again, it wasn't too bad of a tee ball that ended up out of bounds. So I just tried to tell myself that I've been driving the ball really well and continue to. If you're putting it in play off the tee here, you're going to get some wedge opportunities."

For the second week running, Open champion and world No 22 Lowry was inexplicably put out in a low-key three-ball on the back nine with Pat Perez and Keith Mitchell but failed to reproduce the form that gave him a share of third behind C.T. Pan last year.

After opening with ten successive pars, the Offaly man (33) bogeyed the second, third and fifth en route to a 74.

He hit a poor lay-up and took six at the 506-yard second before poor tee shots at the third and fifth led to further bogeys.

It was even more frustrating for McDowell, the 2013 champion, as mixed two birdies with four bogeys and a double en route to a 75

A birdie four at the second left the 2010 US Open champion level for the round with seven holes to go. 

But he failed to get up and down for par after missing the third green, found water and double-bogeyed the 185-yard fourth, missed good chances inside 10 feet at the fifth and sixth and then bogeyed the eighth after a poor pitch.

As for co-leader Poulter, the Englishman feels for fellow Europeans Tour members who, unlike PGA Tour and Korn Ferry Tour players, are not earning world ranking points as they wait for the circuit at home to start again.

"I sympathise," he said. "I don't know what the right answer would have been, but, again, if you don't play for any points and somebody wins the first two events, with this many points on the table, I potentially could move from, say, 60 in the world to top 20 with two wins. So it wouldn't be fair if I was in that position either."

Power cut in Florida

On the Korn Ferry Tour, West Waterford’s Seamus Power improved by nine shots on his opening 78 but missed the cut in The King & Bear Classic at World Golf Village.

The West Waterford man shot a 69 to finish on three-over-par, nine shots outside the cut line at the St Augustine venue in his first start for four months.

Vince India (63-66) and Brett Coletta (63-66) lead by one stroke on 15-under par from Mickey DeMorat, Justin Lower and Dawson Armstrong.