As most eyes were on Lee Westwood and Paul Casey among a 10-strong English contingent in the build up to the season’s opening major, Rose was barely mentioned.
One of the reasons for that was the fact the Olympic champion hadn’t played since withdrawing after two rounds in the Arnold Palmer Invitational at Bay Hill a month ago due to back spasms.
Rose was still off the radar after covering the first seven holes in two-over-par, but talk about a spectacular turnaround.
Sparked by an eagle-3 at the eighth, the 40-year-old covered the last 11 holes in a sensational nine-under to card a 65, beating his previous best score at the Georgia venue by two shots.
The sensational effort on a firm and fast course earned Rose a commanding four-shot lead, bettered only by Craig Wood way back in 1941, when he led by five strokes after the first day and went on to win.
American Brian Harman and Japan’s Hideki Matsuyama fared best of the rest with a 69, one better than a group that includes 2018 winner Patrick Reed and South African Christiaan Bezuidenhout.
Open champion Shane Lowry, 2015 winner Jordan Spieth and Englishman Tyrrell Hatton were also among just 12 players to break par with 71s, but the day belonged to one man.
“I didn’t panic - that was the most important thing,” said Rose, a runner-up in this event in both 2015 and 2017, of how he responded after dropping shots at the opening hole then the seventh.
Back working with Sean Foley, the leader backed up his eagle from around 10 feet by knocking his approach close at the ninth then adding birdies at the 10th, 12th, 13th, 15th, 16th and 17th as he stormed home in 30.
It’s the fourth time he’s either led or been a co-leader after day one in this event, tying for that record with six-time winner Jack Nicklaus.
In addition, this is the sixth time in his career that South African-born Rose has led or co-led here, which is the most of any player in the tournament’s history without a Green Jacket victory.
“You can't win the golf tournament today. Even with a 65 you can't win it today. You can only probably lose it today, obviously,” he said.
“I reset (after seven holes) and thought if I can get myself back around even par, you know, that would be a good day's work.
“So obviously the eagle, boom, straight back in there, and I guess almost just piggybacking with a birdie straightaway at No 9, suddenly I turned in one-under, and I could feel like I could actually leave the front nine behind as a job well done and kind of move to the back nine and try and build a score.
“From that point on I kind of was aware that the lead was only three, and if I played a decent back nine it was basically a very good day's work.
“And then I just got on a great run and was just trying to stay out of my own way and just try to get it to the clubhouse and keep doing what I was doing.
“I putted the ball beautifully and read the greens unbelievably well. If you had said to me walking up the 8th hole, I'd have said no chance, this course is playing a little too tricky for that. But it's incredible. It's a good reminder that you just never know what can happen out there, just to stick with it on the golf course.”
Defending champion and world No 1 Dustin Johnson opened with a 74, as did Scottish pair Bob MacIntyre and Martin Laird.
Helped by a hole-in-one at the 16th, Tommy Fleetwood signed for the same score, while US Open champion Bryson DeChambeau and career grand slam-chasing Rory McIloy both had 76s.