Padraig Harrington, Shane Lowry and Seamus Power all begin at Monterey Peninsula while Graeme McDowell's first round is at Pebble Beach.
Indeed, McIlroy birdied all four of the Par 5s at Spyglass Hill - traditionally the toughest of the three courses used in the tournament - as he stayed very much in touch with clubhouse leaders Kevin Steelman (seven-under-par 65 at Spyglass Hill) and Beau Hossler (65 at Pebble Beach).
World No.1 Dustin Johnson got his tournament off to a flyer with a 67 at Spyglass Hill placing him at five under, and he shares sixth alongside leading Australian Cameron Percy (66, Monterey Peninsula Country Club). He followed his lone bogey of the day with back-to-back birdies at 16 and 17, and picked up three more birdies coming in.
He said: "I've been hitting the ball beautifully".More news: Omarosa: Many people want to stab me in back
Johnson said he's approaching the form that saw him win three straight tournaments early past year before he fell on some stairs and hurt his back as he prepared to tee it up in the Masters.
Rory McIlroy says he is comfortable with his current game.
I feel like I've made good strides with my putting over the off season. This year it's going to be a little different because the weather's so good and the course is playing firmer, I think it will move quicker than last year when we were walking with umbrellas.
A two-time victor of the PGA Tour event, Johnson started on the back nine and holed five birdies, before three in four helped him into the lead.More news: Cavs' Actual Return for Kyrie Irving Revealed After Isaiah Thomas, Other Trades
However, the 24-year-old Texan is confident he will make improvements soon as he looks to defend his Pebble Beach Pro-Am title this week. "But now the scores are starting to come out, I'm able to get out of the mechanics of it and just start playing the round and hitting shots".
World number two Jon Rahm of Spain had five birdies without a bogey in his five-under par 67 at Pebble Beach on Friday.
McIlroy was four-under through 15 holes before suffering a bogey on the 16th, when his wayward drive finished in a waste area.
He was one-under for the tournament, with work to do on Saturday to make the 54-hole cut.More news: Joaquin Phoenix to play The Joker