McIlroy would complete a career grand slam with a Masters victory.
"It was OK," McIlroy said. "I held it together well. It was a little scrappy. The conditions are tricky. Hard to fully commit to shots out there at times just because the wind is - if it's across, it feels down at one point and then into. It's hard to commit to where the wind direction is at times."
There were worrying signs early in McIlroy's round, where on the par-5 second he drove off the tee into the trees and then, after laying up, put his third shot into the crowd behind the green and ended with a bogey.
He bounced back with a birdie on the par-4 third but another bogey followed on the par-3 fourth, hinting at perhaps another messy start to a tournament where he has missed the cut in two of the last three editions.
But a birdie at the eighth saw him enter the turn level and birdies on the 12th and 14th promised better only for a bogey on the 17th, after some missed birdie opportunities, left a slightly sour taste.
"I think after the slow start sort of making a few birdies around the turn was good," McIlroy said. "A little wasteful coming in. I had a good chance for birdie on 15 in the middle of the fairway and didn't take that. Missed a shortish one on 16 and then the bogey on 17. Probably turned a 3-under into a 1-under there at the end.
"But overall still not a bad score, and obviously a lot of golf left to play."
McIlroy was grouped with Xander Schauffele and world number one Scottie Scheffler, who shot a six-under 66, to sit just a stroke off leader Bryson DeChambeau after 18 holes.
Scheffler's bogey-free round was exactly the kind of consistent, calm golf that McIlroy is aiming to produce himself in Friday's second round.
"You just focus on your own game (but) it's great to play alongside Scottie, who is the best player in the world right now, and to see how he is getting himself around the golf course," he said.
"If you look at Scottie compared to the rest of the field, the amount of bogey-free rounds he plays and he shoots is phenomenal, and that's the secret to winning major championships and winning big-time golf tournaments is more limiting the mistakes rather than making a ton of birdies.
"I made three bogeys today, which is fine out there in these conditions, but I just need to tidy it up a little bit to try to keep up with him."
