Shane Lowry has a golden opportunity to win on the PGA Tour for the first time since 2015 and set himself up for the next two years when he chases down world number one Dustin Johnson in the final round of the RBC Heritage.

The world number 50 is just one stroke behind Johnson on nine-under par, tied for second with Ian Poulter and Rory Sabbatini after carding a level par 71 in the third round at Harbour Town Golf Links.

The Offaly man (32) opened up a three-stroke lead over Johnson with nine holes to go when he birdied the second and fifth and then made a 35 footer at the ninth, But with the wind gusting through the pines, he bogeyed the 13th after coming up short in a bunker, then did well to salvage a bogey from 25 feet after finding water short at the par-three 14th.

Having made just one bogey in his first 48 holes, he made his third in four holes when he bunkered his approach after losing his drive well right on the 16th.

But he was upbeat after he parred the last two holes and ranked third for scrambling (16/19), sixth for strokes gained tee to green, seventh for strokes gained off the tee and 14th for strokes gained putting, he knows he has the game to produce a competitive 72-hole aggregate

"Even making those bogeys, it was the best I've been in a while," said Lowry, who could rise as high as 26th in the world with a win and secure spots in the US Open at Pebble Beach, The Open at Royal Portrush and next year's Masters with a win. "So I just want the same tomorrow."

He described his bogey save at the 14th as "huge" and insisted he'll be "very relaxed" when he joins Sabbatini in the penultimate two-ball behind Johnson and Poulter today.

"I didn't hit it as well off the tee and it was just tricky," he said of his third round performance. "I felt good out there. I felt like I hit some nice shots and just didn't get rewarded. It's close enough to 25 mile an hour among the trees. You don't know what it's doing.

"I felt like I had it going early, but I felt like I was happy with what I was doing. So I'm happy to be just one shot off the lead and I'm looking forward to tomorrow."

Seamus Power is also well-placed, tied for 20th on five-under after an excellent 68.

It’s finally coming together,” said Power, who started on the back nine and turned in level par before making an eagle at the second and a birdie at the fifth to move 22 places up the leaderboard. “Another good one needed tomorrow.”

Graeme McDowell bogeyed the last two holes of his weather-delayed second round to make the cut on three-under after a 71. But he could only manage a 73 in the afternoon, and goes into the final round tied 47th on one-under.

Lowry had two holes of his weather-delayed second round to complete early on Saturday and closed with two pars for a 68 that left him one stroke clear on Trey Mullinax on nine-under.

But it was a grind for much of the afternoon and with the wind gusting on the back nine, he was relieved to finish with a fine up and down at the 18th, where he went over the green but almost chipped in for birdie.

"The round out there felt like it was one of those days where we played the first six holes in over two hours, and it was just becoming a long day," he said. "Back to twosomes tomorrow, and hopefully I can get out and play decent tomorrow."

On his plans for the final round, he said he had no plans to do anything different — find fairways and then chip and putt if he misses a green.

"Just what I've been doing all week," he said." I feel like my game is in good shape. I feel like even when I miss a green, I can chip it up. Just kind of take care of my own business.”

Johnson, who hails from South Carolina, will be the favourite to secure his 21st PGA Tour win, especially if he putts as well as he did on Saturday.

He made 160-feet of putts in a three-under 68 — the highlight coming at the 14th where he hit a 50 footer too hard but watched it slam into the back of the hole, run around the rim of the cup and then drop.

"Yeah, it was going a little too fast," the laconic Johnson conceded afterwards. "It was on a good line, it just went in a little too hard and caught the hole and went in somehow. But it wasn't my best, and it went in."

As Poulter recovered from driving out of bounds left at the first and followed a double bogey there with six birdies for a 67, Sabbatini shot 68 to join the Englishman and Lowry on nine-under.

Patrick Cantlay is one of six players lurking just two strokes off the pace on eight under but Johnson remains the man to beat after compiling a 68 despite hitting just five of 14 fairways.

"The course played tough. It was very challenging," said Johnson, who made six putts outside 12 feet, including a 20-footer for birdie on the sixth, a 19-footer for birdie on the 13th and that long bomb at the 14th.

He gave the field some hope with back to back bogeys at the 16th and 17th but like Lowry, he knows that if he can put the ball in position off the tee today, he will be tough to beat.

"You're just trying to put it on one side of the fairway or the other," he said. "Hopefully, if I can drive it well tomorrow, I think I'll be okay."

As for Poulter, he's relaxed and not putting himself under pressure.

"It's not about the win, it's about being in contention, which I've done a lot this year," he said. "I feel great about my game and I'm just going to go have some fun. My dad is here watching me play. And see if we can go out and do it."