Defending champion Graeme McDowell battled his way through the field in the third round of the US Open last night but confessed that catching Rory McIlroy today was mission impossible.

The 31-year old Ulsterman carded a two under par 69 in hot and humid conditions on a golf course softened again by heavy early morning rain to get back to level par for the championship.

When he finished he was 12 strokes adrift of his pal McIlroy and wondering what might have been if the Holywood idol hadn’t hit such a spectacular streak of form.

“If it wasn’t for one man I’d be in with a shout here,” said McDowell, who had an eagle, three birdies and three bogeys in his round. “Rory is putting on a display out there. He’s potentially the next Tiger Woods.  He’s that good.  It’s great to see him out there fulfilling his potential.

“Will he achieve what Tiger was doing around 2000, 15 major championships to date or whatever he’s got?  Can he be that good?  Yeah, potentially. He’s got that potential.”

He added: “I have played a lot of golf with Rory over the last three or four years and said many time he is one of the most phenomenal players I’ve ever seen; he may be hands down the best player I have ever seen.

“Obviously we were disappointed for him at Augusta but what he has done this week has been an accident waiting to happen. He’s been threatening to do this for many many years and it’s great to see him out there fulfilling his potential.

“He’s 22 years old and he’s got a great attitude to the game. Rory McIlroy’s attitude and the way he carries himself on the golf course is the way everyone should try to be.

“He’s got that bounce in his step. It’s easy to bounce around the golf course when you hit it like he does.”

After opening with six regulation pars, McDowell three-putted the par-three seventh for a bogey and appeared to wake up after that.

After a birdie at the short eighth, he hit a five-wood to the heart of the par-five ninth and sank a 30 footer for eagle there to get back to level par for the championship.

He then parred the four opening holes on the back nine but as Rory McIlroy prepared to tee off, he picked up another shot at the 14th to go three under for the day.

The remainder of his round was a rollercoaster affair as he bogeyed the 15th, birdied the par-five 16th but then bogeyed the 17th before closing with a par-four at the tough 18th.

“I made a nice eagle on nine. I hit a great five wood over the flag. My putter has been a little cold the last few days and it was nice to knock one in there on nine.

“It’s tough going out there some many shots behind. Level par going into a US Open on Sunday is normally in decent position but Rory is going to be tough to catch.”

Padraig Harrington had given up all hope of victory as he went into the third round tied for 33rd with McDowell on two over par. But he won’t have been pleased to card a one over 72 to slip from tied 33rd to 38th on three over.

“I am only interested in winning,” he said pointedly after Friday’s second round. “It ain’t going to go down on my CV, making the cut.”

After opening with five straight pars yesterday, the 39-year old picked up two shots on his front nine when he birdied the sixth and then holed an eight footer at the short, par-four eighth to get make to level par and tied for 17th.

It could have been a hat-trick of birdies had he holed a tricky eight footer at the par-three seventh but his putt missed on the low side. He was soon sent scuttling towards the back of the field on four over when he dropped four shots at the start of the back nine.

After bogeys at the 10th and 11th, he made a double bogey six at the 12th - a hole he had birdied from no more than a foot on Thursday and Friday - and closed by sandwiching a bogey at the 15th between birdies at the 14th and 17th.