KIAWAH ISLAND, SC - MAY 21: Padraig Harrington of Ireland hits out of a bunker on the third hole during the second round of the 2021 PGA Championship held at the Ocean Course of Kiawah Island Golf Resort on May 21, 2021 in Kiawah Island, South Carolina. (Photo by Darren Carroll/PGA of America)

Rory McIlroy was left wondering what might have been after he bogeyed his last three holes and produced another disastrous showing on the par-fives to slip eight shots behind halfway leaders Phil Mickelson and Louis Oosthuizen in the PGA Championship at Kiawah Island.

The Holywood star bogeyed three of the four par-fives in a first round 75 before making another two bogey sixes in level par 72 yesterday, leaving him three-over for the three-shot holes.

His par-five tally was nine strokes more than Mickelson (50), who set the target at five-under with a marvellous 69 in the morning wave and seven worse than South African Oosthuizen, who shot 68 to join the left-hander in the lead, one stroke clear of Brooks Koepka (71).

Even though McIlroy missed missed five birdie chances between 10 and 15 feet on his front nine and followed an opening birdie with a bogey six, he rolled in a 16 footer at the sixth and 26 footer at the ninth to turn in two-under par.

He picked up a two-putt birdie at the 582-yard 11th to join Pádraig Harrington and Shane Lowry inside the top 20 on level par.

But just when he looked to be cruising into contention, he missed a four footer for par at the 600-yard 16th, failed to get up and down from sand at the 17t, then tugged his approach into trouble at the last and dropped another shot.

He knows he must cut out his “silly mistakes” and go low at Kiawah Island today after his 72 left eight strokes behind leaders Phil Mickelson and Louis Oosthuizen on three-over.

“I played well, I just didn't get a lot out of the round, “ said McIlroy. “Sort of kept it together, and sort of just let it go there the last three holes.

“I haven't played the par-5s well this week. That's been the big thing. If I'd have played those better, I'd have been right up there, but making five bogeys on the par-5s is not going to get it done.

“I hit the ball much better. I drove the ball much better, I hit the ball much better. So if I can keep doing that, just sort of try to keep the silly mistakes off the card, hopefully get out early when there's not as much wind, and try to post a good one.”

If McIlroy was hopeful but battered by his finish, Lowry was beaming like a kid on Christmas morning after he survived a bruising battle with the Ocean Course to go into the weekend tied with Pádraig Harrington in pursuit of Oosthuizen and the amazing Mickelson and .

The Clara man was forced to dig deep into his bag of tricks at a windswept Kiawah Island, even escaping from a trip to the beach at the 16th with a miraculous par-five as he conjured up a one-under 71 to Harrington’s frustrating 73 to leave them well in the hunt on level-par.

While the leaderboard is packed, they’re just five strokes behind the magical left-hander Mickelson (50), who birdied five of his last eight holes as he scorched home in 31 strokes for a 69.

He shares the lead with Oosthuizen, who shot 68, one clear of the two-time PGA winner Brooks Koepka, who dropped two early shots at the fourth and sixth but eagled the seventh and 11th and birdied to lead on six-under with Oosthuizen only to struggle coming home.

He bogeyed the 15th and 17th and had to make a 12 footer for par at the last to sit alone in third, a shot off the pace with South African pair Branden Grace (71) and Christiaan Bezuidenhout (70) just two behind alongside Master champion Hideki Matsuyama (68)

While the ltop 24 are covered by just five strokes. Lowry and Harrington are tied 19th on level par behind Oosthuizen and Mickelson, who was remarkable on a course that requires course management and an immaculate short game to deal with the inevitable ups and downs.

The left hander birdied the 11th to contest the lead, then bogeyed the 13th, 17th and 18th to slip back to level before charging up the leaderboard with five birdies in his last eight holes.

"I'm having a lot of fun, and to play well, to know I'm playing well heading into the weekend, to be in contention, to have a good opportunity, I'm having a blast," said Mickelson, who will turn 51 next month. "I'm excited for the weekend. This has been a lot of fun."

It was vintage stuff from the five-time Major winner, who could overtake Julius Boros (48 years, 4 months, 18 days when he won the 1968 PGA) and become the oldest men's major champion tomorrow night.

"I wouldn't put it past him," said a weary Harrington (49) after he came home in a disappointing 38 and got a front-row seat for Mickelson's back nine fireworks. "In the position he is, I expect him to contend, and I wouldn't put it past him being there at the end of the week, for sure.

"I think he has the bit between his teeth. I think he believes he can do it in these conditions, just like myself. I think myself, Phil would find it easier to compete on this style of golf course in these conditions in a major tournament all the time.

"You can be patient on these courses, and obviously, you've got to make a few birdies, but it suits somebody who is a player, somebody who is thinking."

He added: "I'm bullish about where I am, and I'm sure Phil is, too. From watching from the outside with Phil, he's prepared to push no matter what. He's not here to make the cut. Even second would be a disappointment for Phil."

Harrington is by no means giving up on his chance to win a fourth Major and take the Boros record himself at 49 years, 8 months, 23 days.

But as he contemplated throwing away as many as seven shots yesterday, he admitted that compared to his heyday, when mistakes were water off a duck's back, he can ill-afford to be profligate these days.

"I'm afraid that I can't take as many punches," he said. "I can't take as many mistakes. I feel on edge to compete.

"When I play well like today and leave shots out there, I'm thinking, 'Can I afford to do that?' Whereas 2008 I would have gone, yeah, I can afford to do that; I'm going to win.

"It was just so much in your comfort zone, and as I said, then new kids come on the block, and you're looking over your shoulder, and you're wondering is your stuff good enough."

The Dubliner's disappointment was palpable after he cruised to the turn in one-under-par but then made a series of clubbing errors coming home as the pressure of playing on the clock took its toll.

While there were birdies at the second and sixth, he bogeyed the first, fourth and fifth and then three-putted the final green from 25 feet as a possible 68 turned into a 73.

"It was a very disappointing nine holes," he said. "I'm happy with how I'm playing, how I'm swinging and what I see in my game. But I should be three, four-under-par, and even then, I'd be a little disappointed."

Bearded Lowry was grinning like a shipwreck survivor, exhilarated but relieved after being picked up clinging to a log after two days adrift.

"I'm really, really happy it's over," Lowry said, his sunburned cheeks shining. "Long day, man. I was goosed out there today, honestly."

And yet, while Harrington finds it tough to take punches, Lowry (34) knows he can roll with them.

"I know it's going to be difficult, so I kind of put myself in a frame of mind that may be different to other weeks where I accept that I'm going to make bogeys and I accept that I'm going to hit bad shots," he said.

After finishing after 8pm on Thursday, he was up at 4am yesterday for an 8:45 am tee time and jumped comfortably into the top 30 despite hitting just eight greens.

"It's just so hard out there," added Lowry, who started on the back nine with two birdies, then followed three-putt bogey from 70 feet at the 15th with a miraculous par-five after driving onto the beach at the 16th.

After mixing two birdies with two bogeys on his back nine, he said: "Yeah, I'm happy to finish. I'm happy to be on level par. I'm five or six behind. I feel like I'm in a good place going into the weekend."

He was thrilled to see Harrington there beside him on the leaderboard on level par and full of admiration for what the Dubliner and Mickelson have achieved so far.

"Look, Phil is obviously Phil," he said. "He's one of the best players of all time. He's at the top of the leaderboard now. I hope he's not there come Sunday. I hope it's me. Yeah, look, it's great to see him.

"It's great to see Padraig Harrington doing well. Padraig is 50 in August. Could be paired with him tomorrow, which could be good craic. But yeah, it's great to see those boys playing well and out here competing. It just shows you that age is only a number."