Rory McIlroy insisted he can't afford to shoot himself in the foot again after he squandered a great start and ended the opening day five shots behind leaders Kevin Kisner and Thorbjorn Olesen in the US PGA.

The world No 4 raced to within two shots early pace-setter Olesen on two under par with eight holes to play at a punishing Quail Hollow but dropped three shots coming home and signed for a 72 that leaves him tied for 33rd with career Grand Slam chasing Jordan Spieth on one-over par.

“It was okay,” McIlroy said. "I started well, two-under through 12, coming through part of the course where you’re looking to pick a couple of shots up on 13, 14 and 15 and I played that stretch of holes in three-over.

"So if I just could have had that three-hole stretch back, but I think other than that, I played nicely. Did what I needed to do. Birdied the par-fives, birdied the holes that you should birdie."

Believing he will be right in the mix if he can shoot in the 60s today, he added: "I can see a low one out there. It’s just a matter of not shooting yourself in the foot too often like I did today.”

Denmark’s Olesen, 27, holed a 30 footer for birdie at the 18th for 67 at a punishing Quail Hollow before being joined at the top late in the day by 33-year old Kisner.

They lead by a shot from US Open champion Brooks Koepka, Texans Gary Woodland and Chris Stroud, 23-year old Web.com Tour graduate Grayson Murray and 40-year old American DA Points on four-under par.

With Spieth forced to finish birdie-birdie-par for a 72, it was an ultimately disappointing day for McIlroy, who bogeyed the 13th and double bogeyed the driveable 14th before missing three birdie chances inside 20 feet at the 15th, 17th and 18th.

Graeme McDowell posted a battling 73 and Shane Lowry a 74 but Pádraig Harrington made four double bogeys in a 79 as McIlroy frittered away a good start.

The Holywood star opened his account by chipping in for birdie at the third but then bogeyed two par threes in a row, airmailing the 181-yard fourth before flubbing a chip from greenside rough at the sixth.

Despite that, he still looked comfortable and used his driver brilliantly to move back into the red, two-putting the par-five seventh before chipping to three feet at the 349-yard eighth to notch back-to-back birdies.

After getting up and down for another birdie the par-five 10th, he was within two shots of Olesen before finding the firm and fast Quail Hollow greens a handful on the way home.

Forced to hole a slick nine footer for par at the 11th after spinning his 100-yard approach off the green, he made a six footer for another par at the 12th but missed from 10 feet for par at the 13th before running up a disastrous double bogey six at the 344-yard 14th.

The world No 4 tried to drive the green but pulled his three-wood into the lake, then fluffed his pitch after a penalty drop and missed from inside five feet for par.

After missing birdie chances from 10 feet at the 15th and 12 feet at the 17th, he parred the last to finish the day just one ahead of Spieth.

“I'm just disappointed with that three-hole stretch, but I'm right in it," said McIlroy, who complained about the grainy greens was outscored by playing partners Rickie Fowler (69) and John Rahm (70). 

The thick Bermudagrass rough caused major problems but McIlroy found the greens tougher late in the day.

"The greens were difficult," he said. "If you just hit a putt a tiny bit off line, it exaggerated it. It was tough to hole putts this afternoon. 

"Hopefully, the surfaces are a little better tomorrow morning and we can hopefully hole some more putts.”

Spieth showed his trademark grinding qualities to finish birdie-birdie-par for a one-over par 72 after a rare off-day on the greens.

He went out in level par but slipped to three over par after back to back three putts at the fifth and sixth before birdies at the seventh and eighth helped him salvage a 72.

"It was just the putter," Spieth said. "Everything else was fine."

Irish Open champion Rahm was three under with three to go but bogyed the 16th and 17th as Fowler recovered from a triple bogey seven at the fifth by playing the remaining holes in three-under for his 69.

Lowry was one under par with eight to play, but despite dropping four shots in his last eight holes, he was pleased that the battled well.

“God help anyone who doesn’t drive the ball well out there today, it is just so difficult,” said Lowry said, who was frustrated his group was put on the clock on his 11th hole, causing him to make the first of four back nine bogeys there.

“I feel like I played nicely," Lowry said. "The golf course is so difficult, and the greens are so firm that if you put yourself out of position it is just so hard to make pars.

“What pleased me most was how hard I fought out there.”

Fowler, Tony Finau, Jim Herman, Patrick Reed, Paul Casey and Brian Harman posted two under 69s to share eighth place as world No 2 Hideki Matsuyama shot a one under 70 matched by Korea's Sung Kang, World No 1 Dustin Johnson, England's Tommy Fleetwood, Jason Day, Bud Cauley and Louis Oosthuizen.

McDowell was one under after six holes but bogeyed the 17th, first and third before following a birdie at the sixth with a closing bogey.

"I drove it very straight but I drove it very short all day," said McDowell, who holed little on the greens.

"I couldn't get much pressure on the driver, which was a little frustrating,  so I had to play the golf course with a lot of club in my hand, which is obviously difficult. 

"But I actually played, really, really, really well. I hit a lot of quality approach shots and gave myself some looks and couldn't seem to take them. 

"Obviously, I have only played the US Open but watching and reading between the lines, this is the toughest test of the four majors this year. 

"Thankfully it is playing tough because if the boys had been making a ton of birdies, I don't think I really could have competed on this golf course. 

"As though as it is, if I can shoot a couple under tomorrow I think I will be there or thereabouts going into the weekend."

Harrington confessed that his bid for a fourth major win is over for another year after he made four double bogeys in a 79.

The Dubliner (45) was out for the count from the moment he made three doubles in a row on his front nine, posting his highest round in the US PGA since he closed with a 78 in his defence of the Wanamaker Trophy at Hazeltine National in 2009.

“No, I can’t come back from eight over par,” he said after his worst of his 57 US PGA rounds. “I can’t remember making three double bogeys in a row before.

"I had to hole a nice eight footer on the last just to break 80! But it's not as if I am not going to try tomorrow."

The three-time major winner was grinding out a decent round before that front nine triple whammy. 

“I thought the golf course was very tough, but I thought the set it up very fair,” said Harrington who followed a birdie at the third with a bogey at the fifth before making another double bogey at his penultimate hole.

"But if you get out of position, you are in trouble.”

Having holed a 30 footer for par at the 13th, his fourth, Harrington made a six footer for another par at the driveable 14th before disaster struck.

He looked set to make birdie at the 575-yard 15th after a big drive. But after waiting an eternity for the green, he carved his second from a side slope up against a fence 30 yards right of the fairway and had to take a penalty drop, eventually three-putting from just over the back of the green for a seven.

"We waited a long time on the 15th fairway, and when I got over the ball, I didn't realise how much of a side slope I was on," Harrington said. "I wasn't comfortable with it and I hit a bad shot. I should have been making birdie and all of I sudden I make double."

Like buses, golfing disasters often arrive in threes and after playing out of turn as a favour to Davis Love III on the 16th, he got a "mud ball" and flew left into the lake to run up another double bogey.

"That's the nature of golf," Harrington shrugged. "If I birdie 15, then I might have been happy to hit it in the right-hand bunker on 16. But no, I try to hit it in the middle of the green, it's a mud ball, and in trying not to hit it right, I hit it left."

To add insult to injury, Harrington pulled his tee shot into the lake at the par-three 17th and made another double bogey, turning in 42 before battling back to five over with a birdie from eight feet at the third.

He then bogeyed the fifth and made another double bogey at the eighth after taking three to get down from just over the green.

Never a fan of Bermuda rough, Harrington said: "I only made one bogey, but if you do miss the fairway, it really is difficult to predict how the ball will react out of the rough.

“The new grass is very different to when we played the Wells Fargo here two years ago. But that’s golf.“