Justin Thomas, Jason Day, Jon Rahm, Jordan Spieth and Justin Rose could all potentially take over as world number one with a win on Sunday, but Johnson showed them a clean pair of heels.

While Rose and Rahm shot 68s to share 13th and Day a 69, Thomas struggled to a 73 and Spieth a 75 alongside Rory McIlroy, who had to work hard for a 71 that was just a shot inside the projected cut line.

When the dust settled, Johnson was sitting pretty in a six-way tie for the lead with former US Open champion Webb Simpson, Sweden's Alex Noren, Chesson Hadley, Matt Kuchar and Patrick Cantlay, one stroke clear of a six-strong group that included defending champion Si Woo Kim.

He changed to the AimPoint green-reading method after a disappointing putting week at the Masters and got his reward for missing just one green in regulation, making four of his six birdies with putts between 10 and 34 feet as he took advantage of easier morning conditions.

"I felt like it was a really solid round," said Johnson, who started at the 10th and went out in five-under 31 before picking up his sixth birdie at the par-five second.

"I drove it very well and hit a lot of greens. I wasn't too sharp with the irons but I was still on the green and rolled the ball pretty well.

"I felt like all the putts I had to today I had the right reads on, which is something I haven't been doing very well."

As for his world No 1 ranking, he's clearly keen to hold on to it for a 65th consecutive week.

“I definitely want to stay there,” Johnson said. "If someone plays well and passes me, obviously they deserve it. But I'm going to do whatever I can to stay there."

The stellar threeball of Tiger Woods, Phil Mickelson and Rickie Fowler failed to sparkle — the left-hander shooting a ragged 79 to Woods’ erratic 72 as Fowler signed for a 74.

While the top 85 players are covered by just six shots, Woods felt he should have broken 70 despite hitting just four fairways.

"No-one is really tearing this place apart, and we're all pretty bunched together," said Woods, who had to make an 11 footer for bogey at the 18th after driving into the water. "That's what this place allows you to do."

He added: "The way I was feeling today, I should have shot something in the 60s, but I didn't do it."

Unlike Spieth, who started bogey-bogey-eagle-double bogey and found water three times in his first seven holes en route to a disquieting 75, McIlroy got off to a good start.

Starting on the back nine, he birdied the 11th from 20 feet and two-putted the driveable 12th before following a three-putt bogey at the 13th with an easy birdie four at the 16th.

The Co Down man is trying hard to be disciplined on a tactical track that he's trying hard to love.

But he couldn’t resist his attacking instincts at the 18th and pulled a driver into the lake before getting up and down from 110 yards for a bogey five, making a 12 footer.

After taking four to get down from greenside rough at the par-five second, slipping back to level par with a six there, he chipped in for birdie at the fourth but had to work hard to par his way home for his 71 and a tie for 55th

Like McIlroy, Shane Lowry started on the back nine and picked up early birdies at the 12th and 13th before he double-bogeyed the 14th and 17th after tee shots found water.

Turning for home, the Offaly man made a 32 footer for birdie at the par-five second, but he bogeyed the seventh and then drove into the lake at the par-five ninth, finishing with a bogey for a 75 that leaves him tied for 108th.