Rory McIlroy endured a frustrating day in the Memorial Tournament as pal Graeme McDowell stormed into contention for the $7m Italian Open.

The Co Down man’s patience was tested at Jack Nicklaus' Muirfield Village, where he found water three times in the last eight holes and didn't hole a putt longer than six feet as he opened with a two-over-par 74.

He trails Mexico's Abraham Ancer, Chile's Joaquin Niemann and Japan's Hideki Matsuyama by nine shots but it was a happy return to Italy for 2004 winner McDowell (38), who has only just returned to the world's top 200 following his share of 12th at Wentworth last week.

The four-time Ryder Cup player, revived since he was awarded a vice-captaincy by Thomas Bjorn, showed further signs that he's coming back to form as he fired a five-under 66 that leaves him just three shots behind Robert Rock, Laurie Canter and Richard Sterne.

Despite hitting just one of the first eight fairways and having to deal with a two-hour storm delay, he made two birdies and two bogeys to turn in level par before playing the back nine at Gardagolf in five-under.

After his second two of the day at the 186-yard 10th, he bogeyed the 11th but then made another two at the 12th, birdied the par-five 13th and holed his second shot for an eagle two at the 443-yard 14th.

He picked up another shot at the 16th for his 66 as Rock, Sterne and Canter shot 63s to lead by two shots from an eight-strong group that includes  Ryder Cup players Rafa Cabrera Bello, Thomas Pieters, Ross Fisher and Danny Willett.

Paul Dunne, who can secure his US Open spot in Sectional Qualifying on Monday or by making the world's top 60 by June 11, made seven birdies in a rollercoaster 69 to sit a shot outside the projected cut.

As for Pádraig Harrington, he made three birdie twos in a five-birdie round, but finished with a double bogey six for a level par 71.

Italian Open scores

It was a frustrating finish for Harrington, who had battled back to two under after making three bogeys in his first five holes.

But it was arguably more frustrating for McIlroy in Ohio as he had three penalty shots for finding water on the back nine and played the four par-fives in one-over.

He birdied the sixth from just four feet, but could only par the par-five fifth and seventh bogeyed the short eighth, then drove into water at the par-five 11th before saving par from six feet.

A birdie from six feet at the 13th got him into the red but he made a sloppy double-bogey six at the next, finding water left despite taking an iron from the tee before three-putting from 12 feet.

He then hit another tee shot left into water at the 18th and made bogey.

It was also a frustrating day for Shane Lowry, who was cruising at two-under after birdie twos at the fourth and eighth but signed for a one-over 73.

After driving out of bounds at the ninth to run up a double-bogey six, he dropped another shot at the 10th and saw birdie fours at the  11th and 15th  cancelled out by bogeys at the 14th and 17th.

Mexico-born Texan Ancer and former world amateur number one Niemann took advantage of receptive morning conditions to fire seven-under 65s before being joined late in the day by Matsuyama, who birdied four holes in a row from the 13th before holing out from 137 yards for a stunning eagle two at the 17th.

As the round went along, I played better and better,'' said Matsuyama, who got his first PGA Tour win at the Memorial four years ago.

They led by one from Beau Hossler with Tiger Woods seven behind after a grinding 72.

Struggling with a stiff back, Woods bogeyed the par-five 11th (his second), double-bogeyed the par-five 15th after carving a drive out of bounds and then dropped another shot at the 16th to be four-over after seven holes. 

But he birdied the 17th and the second and followed a three-putt bogey at the fourth with three birdies in a row from the fifth to get back to level.

“I fought back,” said Woods (42), who kickstarted his comeback by hitting a spectacular, 247-yard three-iron to the par-five fifth, then birdied the next two holes before getting up and down from 60 yards for par at the last. 

"I wasn't rotating very well. Back was tight but I was able to make a few tweaks in my swing and lo and behold, I was able to make some good swings on my back nine and turn the whole thing around."

He blamed "age and surgeries" for his stiffness, but he was still proud of that three-iron at the fifth and that closing par save.

Four players have a chance to end the week as world No 1 but while current number one Justin Thomas matched Woods with a 72, England's Justin Rose, who will take over with a win, shot 71 as Dustin Johnson shot a 72 and Jordan Spieth a three-over 75.

Scores