Shane Lowry hits his tee shot on the 14th hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

He was leading the US Open but Shane Lowry might have been chatting over the garden gate to a neighbour as he headed down the par-five 12th at Oakmont with a one-shot lead.

“What about Mayo?” he said to an Irish media colleague with a shared love of Gaelic football, shaking his head as they discussed the shock news that the Connacht football kingpins had fallen to a young Galway side on Saturday.

Five minutes later he was tapping in a two footer for his fifth birdie of the round and his seventh of a marathon 32-hole day that ended with him leading the US Open by two strokes from PGA Tour rookie Andrew Landry and by three from Lee Westwood, Sergio Garcia and Dustin Johnson on five under par when play was suspended due to darkness.

World No 1 Jason Day was just six shots on one over par after a third round 66.

“We all know that this course can jump up and bite you in a split second,” Lowry said. “So yeah, I’m two ahead with 22 holes left. Let’s not get ahead of ourselves.

"These are the best golfers in the world behind me, Dustin and Jason. Sergio played lovely today. Like I said, I have to go out and do what I've been doing all week. I’m really looking forward to tomorrow.”

Shane Lowry hits his tee shot on the second hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

Putting his game and his psyche in perspective after a season that has delivered many false dawns, he added: "This is exactly where you want to be. I've been beating myself up over the last six months trying to get in this position. I'm here now. I might as well enjoy it while I’m here."

It was a day that saw Rory McIlroy threaten to shoot a Johnny Miller-esque 63 by racing to the turn in four under par 31 only to limp home in 40 for a 71 to miss the cut by two shots on eight over.

With McIlroy slipping away without speaking to the press, Lowry slipped into the Superman costume with ease.

Shane Lowry hits from a greenside bunker on the eighth hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

In the morning he banked some crucial karma when he called a penalty shot on himself on his seventh hole, the par-three, 16th and did well just to make bogey and slip back to two over for the day.

“I addressed the ball, and the ball moved back,” he said. “I had to penalise myself. It’s very frustrating in a tournament like that.

“I actually holed a great eight-footer for a bogey on that hole. I think, if I had missed that, it would have been difficult to get back from there.”

He fought back with birdies at the fourth and sixth to card a level par 70 to go into the third round tied for third place, two shots behind Dustin Johnson on two under par.

Seven hours later he two putted the 14th for par in fading light to be three under for his third round and two ahead of Landry and three clear Lee Westwood (15 holes), playing partner Sergio Garcia (14 holes) and Johnson (13) on five under par.

Shane Lowry misses a birdie putt on the first hole during the second round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

As an exhibition of ball-striking prowess and cool under pressure, it was a clinic and while he knows he’s being chased down by some of the best players in the world, he is thinking and playing like a man who will be very hard to beat.

“I haven’t felt that comfortable on the golf course for a while,” said Lowry, who bogeyed the second when he spun his approach off the green but then pitched close from heavy rough to birdie the fourth, rolled in an eight footer for a two at the sixth and the rolled home a slick 20 footer he knew was for the outright lead at the seventh.

While he bogeyed the eighth to fall behind, he brilliantly birdied the ninth from six feet, picked up another shot with a trademark wedge to two feet at the par-five 12th to find himself two clear before two-putting for solid pars at the 13th and 14th as play was suspended due to darkness.

Shane Lowry reacts to a missed birdie putt on the first hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

“I’m hitting good shots,” he said of a hugely impressive display. “Myself and Dermot are making good decisions. It is up to us now tomorrow to go out and keep doing what we are doing and not get ahead of ourselves and see what I can do.

“It is an exciting day ahead. I’ve got 22 holes left. If I play as well as I’m playing, God knows where I will be this time tomorrow.”

Lowry’s clear thinking was evident during the morning round when he made some mature course management decisions to avoid making a major mistake.

In the afternoon, he was by far the most comfortable of the leading contenders as Garcia became frustrated by his inability to hole putts and Johnson played his first 10 holes in two over.

When he faced a 20 footer for birdie at the seventh, he was well aware it was to take the outright lead and relished the opportunity to cross a mini-goal off his list.

“I knew Dustin made bogey on the hole before and I had a 20 footer down the hill and I knew that was to take the lead, which is pretty cool,” he said before adding with a grin that his caddie, Dermot Byrne “was trying to talk me down off my pedestal, and then I went ahead and bogeyed the next hole.”

Lowry failed to save par from sand at the eighth but Garcia missed an eight footer to birdie that would have put him one in front.

One hole later, it was Lowry who took advantage of his chance to enjoyed a two-shot swing, firing a glorious eight iron to seven feet and then holing the putt as Garcia found sand off the tee and bogeyed.

Shane Lowry hits his second shot on the third hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

Putting has held him back this year but when asked if he could recall the last time the putter felt so good in his hands, he grinned sheepishly and said: “Quite a while.

“I'm not going to say how much, because I don't want to jinx myself for tomorrow, but I haven't felt as comfortable on the greens in quite a while.

“With me it just depends if I hole a couple of putts and I’ve managed to do that and not make silly mistakes. I just need to do that for another round and a bit.”

Asked if he’d draw inspiration from winning the WGC-Bridgestone Invitational in Akron last August, he said: “I’m sure I will — at certain stages. I’m just going to go out and hit the shots, the same old cliché with golfers. You don’t want to get too ahead of yourself, especially in tournaments like the US Open.

Rory McIlroy hits from a bunker on the 15th hole during the second round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

Graeme McDowell made six bogeys and five birdies in a second successive 71 to share 28th on four over par with Jordan Spieth (72 72 70).

But it was a disappointing day for world No 3 McIlroy, who went out targeting 66 to repair the damage of his opening 77 and birdied the 10th, 12th, 14th and 16th to get back to three over.

A three-putt par from 75 feet at the driveable 17th was a blow, however, and his comeback ended when he four putted the third, his 12th hole, from 15 feet for a double bogey six and never recovered.

Shane Lowry waves to the gallery after making a birdie on the ninth hole during the third round of the 2016 U.S. Open at Oakmont Country Club in Oakmont, Pa. on Saturday, June 18, 2016. (Copyright USGA/Jeff Haynes)

Back to two under for the day and sitting just inside the six over par cut line, he chipped in for a miraculous par four from the upslope of a bunker at the fifth but then missed the green and bogeyed the sixth to find himself right on the cut line.

Needing a par four at the ninth to survive for two more rounds, he fatally found sand off the tee, failed to escape at the first attempt and pencilled in another double bogey six to miss the cut by two.