The young Scot had dropped four shots in a row when he arrived on the 12th tee before showing his mettle by covering the last seven holes for a two-over-par 74.
“It’s been unbelievable, everything I’ve dreamed of,” MacIntyre told Sky Sports Golf afterwards about his first Augusta National experience. “But I’m here to compete now.
“I’m a bit disappointed with my score today, but the way it was going at the turn, I mean I was struggling.
“I wasn’t playing that bad. I was just on the wrong side of some holes and the greens started getting firm and fast. But we hung in and two-over isn’t a bad score.”
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The highlight of the left-hander’s day was a chip-in birdie at the par-4 17th, having earlier birdied the 13th and 15th on the back nine before dropping a shot at the short 16th.
“I was in no man’s land,” he said, smiling, of his sensational shot at the penultimate hole. “I was in position Z for that flag.
“I thought just go for the flop and it came off perfectly. It went straight up under the cap and it was perfect the way it went in.”
MacIntyre secured his place in this week’s field when topping a group that included world No 1 Dustin Johnson in the WGC-Dell Technologies Match Play in Austin a fortnight ago.
“It was huge for the belief more than anything,” he said of that achievement. “I knew I could play good golf, I didn’t know how good my good was, simple as that.
“I went out against DJ and, if you asked me, he did well to get to the 18th and tie me. He played brilliant the last couple holes.
“I took a lot of belief from that. It’s where I want to be. This is the stage I want and the people I want to be playing against.
“I’m here now and I’ve just got to keep practising hard and working hard, just performing on the golf course.”
MacIntyre played nine holes earlier this week with Patrick Reed, the 2018 winner, the pair having struck up a friendship since they played together in the 2019 Turkish Airlines Open in Belek.
“He showed me little tricks with certain pins and Martin Laird also helped me on the front nine as well,” said MacIntyre of the American.
“Patrick has been huge and influential on me. He’s helped me in Europe and America.
“He’s not shy to tell me if I’m doing something wrong and not shy to tell me some tips. He’s been brilliant for me.”
Using his own advice to good effect, Reed opened with a two-under 70 to sit handily-placed at the end of the opening circuit.
“I love this type of golf, especially around here because you have to be creative,” he said. You can't just play golf swing after golf swing.
“You have to start using slopes. You have to play out of different windows into greens.”