Bouncing back from a tough loss last weekend, Johnson began with a 6-under 66 on a sunny Thursday at Muirfield — another brilliant opening after a 65 at Lytham last year.
"I don't know what the secret is," Johnson said. "I hit some nice shots and obviously I putted really, really well."
Now, he needs to finish the job.
A year ago, the 2007 Masters champion followed up with a 74 in the second round on the way to a ninth-place finish.
"This game demands resilience," Johnson said. "That just comes with experience. That certainly comes with embracing what's happened and then also throwing it behind you and plodding along to the future."
The immediate future looks pretty bleak for McIlroy, who only last August won his second major title with a runaway victory at the U.S. PGA Championship. He showed no signs of snapping out of his baffling slump this season, struggling mightily to a 79 that marked the second-worst round of his Open career.
The only time McIlroy shot worse was an 80 at St. Andrews in 2010, but that was more a product of a brutal wind than poor shots.
This time, he could blame only himself. He didn't even beat birthday boy Nick Faldo, who stirred up a bit of a tempest this week when he advised McIlroy to spend more time focused on golf rather than off-the-course pursuits.
Faldo, who turned 56 on Thursday, matched McIlroy's score even though he's barely played at all in the last three years.
No one played better on the front side than Shiv Kapur of India, who birdied six of the first seven holes and made the turn with a 6-under 30, briefly moving to the top line of the leaderboard. But the back nine was playing much tougher, which he discovered right away. He three-putted for double-bogey at the 10th to drop back.
The wind off the Firth of Forth wasn't too much of a hindrance for the morning starters. But the greens were slick as ice, having baked in the unseasonably dry Scottish weather over the past few weeks, and several golfers — Phil Mickelson and Ian Poulter among them — complained about everything from the pin placements to the speed of the putting surfaces.
"The eighth hole is a joke," Poulter said. "The 18th needs a windmill and a clown face."
But McIlroy had plenty of problems just getting to the green.
Time and again, he found himself whacking at the ball out of the rough or trying to escape the treacherous bunkers. His most telling sequence came at the 15th, where he drove it into the tall grass, chopped it out just short of the green, then sent a putt screaming past the flag — right into a bunker on the other side. He let out a sigh that said everything.
"Sometimes I feel like I'm walking out there and I'm unconscious," McIlroy said.
Johnson, on the other hand, quickly shook off his playoff defeat in the John Deere Classic. He didn't arrive at Muirfield until Monday, a day after making bogey on the 72nd hole and losing to Jordan Spieth, who became the youngest winner on the U.S. PGA Tour since 1931.
Johnson got on a roll with an eagle at the par-5 fifth, then birdied the next two holes to claim the top spot on the board.
He was still there when he walked off the green at No. 18.
"If anything from last week, what I've embraced is the fact that I'm playing great and I can put that into play, and I'm certainly somewhat confident in what I'm doing, confident in my routines, confident in my walk out there, confident in my lines," he said.
Mark O'Meara ripped through the front nine as though he was in his prime — not a 56-year-old who has combined to shoot 76 over par in the past decade at golf's oldest major. The Open champion from 1998 at Birkdale made the turn with a 5-under 31 before stumbling a bit with three bogeys on the back side.
But O'Meara rolled in a long, curling putt for eagle at the 17th and finished with a 67, tied with Spain's Rafael Cabrera-Bello at just one stroke off the lead.
Not that it's unusual for an old-timer to play well in the Open. Four years ago, Tom Watson nearly won at age 59. Greg Norman led after 54 holes well into his 50s.
Faldo, a three-time Open champion, hoped to find the fountain of youth when he decided to play at a course where he twice claimed the claret jug. But Muirfield was simply too tough this time.
"I haven't got the touch anymore," Faldo said.
Miguel Angel Jimenez, Brandt Snedeker and Dustin Johnson were right in the mix after posting 68s. Another shot back were major champions Mickelson, Angel Cabrera and Todd Hamilton.
Perennial favourite Tiger Woods was among those playing in the afternoon, when the greens firmed up even more in sunshine so bright it prompted some fans to break out umbrellas to ward off rays rather than rain.
Woods yanked his opening tee shot off a lone tree far left of the fairway. He was forced to take an unplayable lie and settle for a bogey. But a span of three birdies in four holes after the turn left him at 1 under.Suggest a correction