Shane Lowry vowed to fight on after he recovered from a potentially devastating triple bogey at the 17th to card a 69 and go into the weekend nine shots behind leaders Kevin Kisner and Hideki Matsuyama in the weather-delayed US PGA at Quail Hollow.

Putting brilliantly, the Clara man raced to five-under par after 15 holes and was tied for seventh on two-under par before his momentum was halted by an untimely weather delay.

With play suspended because of the threat of lightning, a torrential downpour soaked the course before Lowry returned to play his second to the 16th after a one hour, 43-minute stoppage and made par there before getting distracted on the tee at the 177-yard 17th.

The Green Mile is treacherous at any time and the Clara man stood off his eight iron as a marshal quietened a sparse crowd, then hit "an unbelievably bad shot" 20 yards right into deep greenside rough.

From there he misjudged the lie and chipped through the green into the greenside lake, eventually making a triple bogey six after being forced to play his fourth shot from the drop zone 109 yards away.

“It was only an eight iron and I was licking my chops, thinking, give me another birdie,” Lowry said of the 17th after ending the day tied for 23rd on one-over.

Refusing to blame the delay, he added: "I came out and I hit one bad shot. If I finish bogey-bogey-bogey I would probably be standing here going; I didn’t need that break. 

“The fact that it is just one bad hole and I just need to tell myself that I played 17 great holes and 36 decent holes. 

"If you had given me one over par standing on the first tee yesterday morning I probably would have taken it going into the weekend. 

“That’s the game we’re in, we are dealing with mother nature every week.

“I am here for the weekend, I still feel like I am in a decent position and I am swinging the club well and putting lovely. There are a lot of positives.”

Lowry regrouped brilliantly after his triple bogey, fading a 300-yard drive off the creek left of the 18th before rasping a 198-yard six-iron to 10 feet.

While he missed the putt and signed for a two under 69 that leaves him nine shots behind leaders Kisner and Matsuyama on one-over par, he believes he has the game and the confidence to challenge over the weekend.

“There are 36 holes to be played,” said Lowry, who is ranked second this week for strokes gained putting. “I am hitting the ball well, I am happy with what I am doing and I am in a decent position.

"I am putting lovely. I don't want to tell myself too much but since Augusta I have putted well. And I know I have. And I worked hard on it. 

“I didn't putt well for a good year before that. But I’ve holed a few putts today and I said to Dermot, we might as well take them because there are days when they don’t go in."

Kisner fired a second successive 67 to take the early lead before being joined on eight under par late in the day by Japanese world No. 3 Matsuyama, who blasted a seven-under par, course record 64 that was equalled 15 minutes later by Italy's Francesco Molinari.

Australian Jason Day shot 66 to six alone in third on six-under with Molinari’s 64 leaving him tied for fourth with Louis Oosthuizen (67) and Chris Stroud (14 holes), three shots off the lead on five-under.

Four-time major winner Rory McIlroy had to birdie his 16th and 17th holes to post a second successive 72 having flirted briefly with the cut line after four back nine bogeys in the space five holes.

"I feel a lot better about myself being two-over for the tournament instead of four-over,” McIlroy said.

“I think it's quite a big difference. If I get out tomorrow and get off to hopefully a better start, I feel like I’ll still be right in this tournament."

The Holywood star produced a Seve-like par save at his opening hole - sending a low six-iron rocketing off a cart path, through a bunker and onto the edge of the green after his approach to the par-five 10th careered down the same cart path, 80 yards right of the green.

It was an early moment of magic from the world No 4 but there was precious little else to cheer as he missed eight greens and was ranked 121st for proximity to the hole — 48 feet on average — making it impossible to make birdies.

He’s ten shots off the lead in a share of 31st on two over but Padraig Harrington is two over for his round 10 over for the tournament with two holes to complete on Saturday morning.

The Dubliner will miss the projected four-over par cut alongside Graeme McDowell, who shot 76 to finish in seven over.

Lowry is now the main Irish challenger after a brilliant round that was undone by the weather and a momentary lapse in concentration.

He birdied the fourth to turn in one under par, then converted from eight feet for birdie at the 10th, made a 20 footer at the 11th, saved par from 14 feet at the 12th, knocked in a seven footer for birdie at the driveable 14th and chipped dead to set up a tap in birdie at the par-five 15th to get two under.

Despite his finish he was still happy with his first two rounds and confident he can make a move over the weekend if he continues to putt well.

He came into the week struggling for confidence after missed cuts in the Open and the RBC Canadian Open, confessing he needed a motivational chat with mental coach Gerry Hussey because he had no desire to pick up a club and practice.

Bemused by the ups and downs of the game, Lowry said: "This game puzzles me every day of the week. Even on one of my best days of the year, I am still disappointed coming off and that’s what this game does to you. 

"I can’t explain what this game does to you, it is mentally very challenging but I am a fighter. I will fight on and I will work hard and I will stick my head down and I will grind as hard as I can and I will do alright.

"I'd be fairly confident going into the weekend but it is all about going out there and parring the first and getting on it from there."

Asked how the course and the greens might play today, he said: "They will turn on that SubAir tonight and they will be like bricks in the morning again I'd say." 

As for McIlroy — ranked 128th of the 130 PGA Tour pros in the field from between 100 and125 yards — he was bullish about his chances of making a weekend comeback but will need to hit more fairways and improve drastically with the putter. 

The world No 4 turned in one under par to be level for the championship but dropped four shots in five holes from his 11th to teeter on the cut mark before finishing birdie-birdie-par from the seventh.

Asked if he saw a “low one” out there, he said: “Yeah, but I guess a low round used to be a 61 or a 62. A low round now is a 66 or a 67. 

“You're playing your ass off to get that. I’d say, if I shoot two 67s over the weekend, I'm going to have a really good chance.”

Before the horn sounded to suspend play for the day shortly after 8:10, players raced to hit their tee shots so they could finish their rounds. 

Day was fortunate the Dustin Johnson did him a favour at the 18th, hitting off first so they did not have to return to the course early today.

With the rain taking all the sting out of the course, the late starters made hay in the softer conditions, leaving Lowry and McIlroy with a lot of work to do today.