Johnson’s position at the top of the rankings, which he has held since February last year, is under threat from Justin Thomas, Jon Rahm, Jordan Spieth and Justin Rose this week.
But the former US Open champion is not about to make life easy for his rivals and carded six birdies in an error-free first round to share the lead with compatriots Webb Simpson, Chesson Hadley, Matt Kuchar and Patrick Cantlay and Sweden’s Alex Noren.
Rose and Rahm are just two shots off the lead after rounds of 68, but Thomas could only manage a one-over-par 73 and Spieth struggled to a 75 which featured four bogeys, a double bogey and an eagle on the short par-four 12th.
“I haven’t had the best record here but it’s a golf course that I like, I enjoy playing it and I feel like I should play well here,” Johnson said after his lowest score and first bogey-free round at Sawgrass in 31 attempts.
“My expectation is the same for every tournament, I want to play well and put myself in a position to have a chance to win on Sunday.”
Asked about the world ranking situation, Johnson added in a post-round interview broadcast on the PGA Tour’s Twitter account: “Justin [Thomas] has been pretty close to me for a while. Every week I know there’s a chance that someone can pass me.
“I definitely want to stay there, but if someone passes me it’s not going to change anything, I’m still going to go back the next week and try to get it back. It was a big deal to get there and it’s a big deal to stay there. I like being number one so I want to stay there.”
Rose, who was playing alongside Tommy Fleetwood (69) and Ian Poulter (70) in an all-English group, was frustrated not to make more of a brilliant beginning to his round.
The Olympic champion started on the 10th and followed a birdie on the 11th by holing out from 96 yards for an eagle on the 12th, but then mixed three bogeys with four birdies.
“It was obviously a dream start but I didn’t make much of it from that moment on,” Rose told Sky Sports. “The 12th is a fun little hole, a risk-reward hole, and normally if you make eagle you think you’re going to have a crack at the green.
“But I liked where the pin was today, there’s a really tough slope that’s about six, eight feet to the right of the pin that makes chipping to that pin incredibly difficult and very inviting for a wedge shot.
“And I knew that I could put the wedge in there just a little bit to the right of the pin and let it spin down. As it happened I hit my wedge straight at it and it took one bounce, checked and went in.”
Former champion Sergio Garcia held the lead on seven under par before dumping his tee shot on the par-three 17th - where he made a hole-in-one in the first round last year - into the water to run up a double bogey, with a bogey on the last leaving the Spaniard on four under.
But the marquee group of Tiger Woods, Phil Mickelson and Rickie Fowler fared even worse, Woods carding an eagle, two birdies and four bogeys in a level-par 72, Fowler returning a 74 and Mickelson a nightmare 79 after playing the last five holes in seven over par.
Martin Laird had an up-and-down day, carding an eagle and four birdies but also a double-bogey and four bogeys as he carded a level-par 72.
Russell Knox, the other Scot in the field, managed just one birdie - at the par-5 ninth - as he posted a 74.