Taking up where he’d left off when finishing with a flourish in The Masters in April, two-time winner McIlroy signed for seven birdies, including four in a row on his front nine, in the opening circuit of the season’s second major at Southern Hills in Tulsa.
On a day when the early starters enjoyed easier conditions before a gusting wind got up in the afternoon, the effort earned the Northern Irishman a one-shot lead over American duo Will Zalatoris and Tom Hoge.
Justin Thomas, the 2017 winner, coped best later in the day to card a 67, matching an earlier effort from Matt Kuchar, with others off to promising starts including Olympic champion Xander Schauffele and Cameron Smith as they both signed for 68s.
It was McIlroy’s best first day’s work in a major since the 2011 US Open at Congressional, where he burst out of the traps with the same score and went on to win that event by eight shots.
That was one of three occasions that he’s opened with a 66 or better and kicked on to land majors, having also used strong opening salvos to triumph in both The Open and PGA Championship in 2014.
The latter was McIlroy’s most recent major victory, but, on this evidence, he could be about to use 2022 as a kick-start in the events that matter most to him.
The 33-year-old is relishing a trip to St Andrews in July for the 150th Open, having missed out due to an untimely injury in a football kickabout when he was due to be the defending champion there seven years ago.
First and foremost, though, he’s excited about what lies ahead for the next three days after outshining both Jordan Spieth (72) and Woods (74) in their marquee group.
“It was a great start to the tournament,” admitted McIlroy. “I've been playing well coming in here. I've been carrying some good form.
“Obviously that took a lot from that last round at Augusta (a 64 that was rounded off with a holed bunker shot), played well up in D.C. at the Wells Fargo there, and played good in the practice rounds earlier this week.
“I think when your game is feeling like that, it's just a matter of going out there and really sticking to your game plan, executing as well as you possibly can, and just sort of staying in your own little world. I did that really well today. It was nice to get off to that good start and sort of keep it going.
“I feel like this course, it lets you be pretty aggressive off the tee if you want to be, so I hit quite a lot of drivers out there and took advantage of my length and finished that off with some nice iron play and some nice putting.”
McIlroy ignited his day with those four straight birdies from the 12th before adding further gains at the second, fifth and ninth. His two dropped shots both came at par-3s - the sixth and eighth.
“When you get off to a good start like that, sometimes you can maybe start to be a little careful or start to give yourself a little more margin for error, but I stuck to my game plan,” he added.
“If I was disappointed with anything, obviously the two bogeys on the par-3s on the front nine, but it's very easy to make bogeys out here. You get yourself just a little bit out of position.
“I didn't encounter too many of those tricky scenarios today, but it can certainly be tricky. You get yourself out of position here, you just try to make a 4 or a par and run to the next.”
On his return to the venue where he won the same event in 2007, Woods started with a birdie that was set up by a delightful approach at the tenth, where he’d politely asked a camera operator to “give me some breathing space” after getting too close as he walked down a hill from the tee.
Woods, of course, is making his first appearance since returning to major action in The Masters following the car crash that left his right leg seriously damaged and, to the delight of a huge crowd, he then birdied the 14th as well.
However, the 15-time major winner then made four bogeys and one birdie in eight holes around the turn before finishing bogey-bogey, admitting afterwards that he’d struggled physically.
“My leg is not feeling as good as I’d like it to be… we just need to start the recovery process and go after it tomorrow,” said Woods.
“Well, I just can't load it,” he added in explaining how he’d been impacted. “Loading hurts, pressing off it hurts, and walking hurts, and twisting hurts. It's just golf.”
Woods went on to say it had been a “frustrating day” in terms of his performance. “Drove it well,” he observed of an effort that marked his worst start in the event since an opening 75 in 2015, “but my iron shots were not very good. I didn't get the ball very close.
“I got off to a great start and didn't keep it going. I really didn't give myself any looks for birdie. I was struggling trying to get the ball on the green, and I missed quite a few iron shots both ways.”
According to McIlroy, it had been easier on this occasion to play in the same group as Woods than he’d encountered in the past. “It's different playing with him here than it is say at East Lake, because East Lake feels so claustrophobic, the crowds are so much more on top of you,” he said.
“Here it's big wide corridors. I feel like there's a lot of room, so it doesn't feel as oppressive as some other venues. I was looking forward to the draw anyway. It's always a cool group to be a part of. But I think this golf course just with how it's been opened up, it doesn't feel quite as boisterous as it usually does.”
Zalatoris enjoyed a career-best day on the greens, holing putts totalling more than 150 feet of putts, while 2022 AT&T Pebble Beach Pro Am winner Hoge signed for five birdies.
Thomas posted his best opening-round score in seven starts in the event, but, in contrast, it was a day to forget for two-time winner Brooks Koepka as he struggled to a 75.