The 21-year-old from Northern Ireland demonstrated all the poise of a seasoned professional as he stormed to the top of the leaderboard with seven birdies on a perfect day at Augusta national.
His 65 was by far his lowest score in seven competitive rounds at the Masters, reinforcing his status not only as one of the most talented players in the game but also one of the fastest learners.
"I'm still relatively inexperienced but I feel as if I'm a pretty quick learner. I'm getting there," said McIlroy. "There's no substitute for experience, especially in major championships, and I still feel as if I have a lot of learning to do."
Two years ago, McIlroy finished tied for 20th in his first appearance at the Masters but did not break 70 in any of his four rounds. Twelve months ago he failed to make the cut after shooting rounds of 74 and 77.
McIlroy has been on a steep learning curve for most of the past two seasons. He has not won a major but has finished in the top three in three of the last five majors.
But perhaps the most important lesson came at last year's British Open when he shot a 63 in the first round to match the lowest score in any of golf's majors, but blew his chances of winning when he carded 80 the next day.
He fought back impressively over the weekend to finish tied for third but vowed never to make the same mistake again.
"It was a very valuable lesson in my development as a golfer ... and I'll be thinking about how I can do things better tomorrow than I did that day in St Andrews," he said.
McIlroy doesn't expect to fall apart on Friday.
"I have that experience to draw on," he said, "especially being in a similar position to last year at St. Andrews. I feel like I'm better prepared to tee off in the second round of a major with the lead."
Tiger Woods wasn't anywhere near the lead, but at least he wasn't totally out of it. Mired in the longest winless streak of his career, he made a long putt at No. 14, lipped out several others and finished with a 71.
He considered it a promising start.
"I'd rather be where Rory is," Woods said, glancing at the scoreboard from behind the 18th green. "But, hey, there's a long way to go. We've got a long grind ahead of us. ... I'm very pleased. I'm right there in the ballgame. I'm only six back."
While Woods has gone 20 tournaments over 17 months without a win, he's always a contender at Augusta National, where he's captured four green jackets and finished fourth a year ago.
Defending champion Phil Mickelson teed off in the next-to-last group and pushed his opening tee shot into the trees left of the fairway. He scrambled to save the first of seven straight pars, before a birdie at No. 8 pushed him into the red for the first time.
Mickelson was coming off a three-stroke win at Houston, his first triumph since last year's Masters and a sign that his game was peaking at just the right time.
Former U.S. PGA champion Y.E. Yang was closest to the lead, dropping to 6 under with an eagle at the par-5 13th. Matt Kuchar shot 68, while four other players were at 69: Sergio Garcia, Charl Schwartzel, Brandt Snedeker and Ross Fisher.
Two-time U.S. Open winner Retief Goosen had the early lead after holing out an eagle from the fairway on the first hole. But the South African limped to the finish with three straight bogeys for a 70 that felt much worse.
US PGA champion Martin Kaymer came in as the world's top-ranked player, but he's never made it to the weekend at Augusta. It looks like the German will be going home early for the fourth year in a row, opening with a dismal 78 - his worst score yet in the Masters.
"For me, it was very difficult," Kaymer said. "There's some golf courses that suit you and some, they just don't."
Lee Westwood is a former No. 1 in the second spot behind Kaymer. The Englishman is regarded as the best player never to win a major, an unwanted distinction he'd sure like to erase from his record. He has some work to do, too, bogeying the final hole for a 72.
The day began shortly after sunrise with Jack Nicklaus and Arnold Palmer striking ceremonial tee shots, the traditional start to the year's first major.
With the overnight chill still lingering, the 81-year-old Palmer hit a little fade that stayed in the fairway. The 71-year-old Nicklaus went next, ripping one right down the middle about 30 yards past his longtime rival.
"I guess it's still kind of fun to lop it off the first tee and be part of a great event," Nicklaus said. "People enjoy it. It's Augusta's way of honoring its past champions and people such as Arnold and myself. It's really quite nice they allow us to do this."
