But, at the same time, the Oban man acknowledged it had still been a solid start in his bid to extend a run of making the cuts in majors to nine out of nine.
Out in the first group from the tenth tee, MacIntyre led the season’s second major at one point as he played beautifully on his opening nine.
Giving himself lots of birdie chances, the left-hander birdied his opening hole from 14 feet before making a second gain from seven feet at the par-5 13th.
Facing his first test of the day, he holed an eight-footer to save par at the 15th then played a delightful flop shot at the next after coming up short right with his approach.
Polishing off an impressive outward journey, MacIntyre knocked in a five-footer for par at the 17th before two-putting from 50 feet at the 18th to turn in 33, two-under.
His first dropped shot came at the first, where the flat stick was unable to save him on this occasion. Six pars followed before a second bogey followed at the par-3 eighth, though the sting from that was eased a bit by a seven-footer saving par at his closing hole.
The effort left MacIntyre tied for 27th, five shots behind leader Rory McIlroy, in a group that includes former Open champions Francesco Molinari and Shane Lowry, as well as Viktor Hovland and Tyrrell Hatton.
“We got nice weather to start with, not much wind, and I took advantage,” said MacIntyre afterwards. “Hit a nice second shot into my first hole, the 10th. Managed to make a good putt and just got it rolling from there.
“I didn't really miss a shot on the front nine. Easy going. I probably should have been a couple more under.
“Then, on the back nine, it was a lot tougher, a lot longer holes, a lot more crosswinds. But, overall, we’ll take level par.”
He said that his bogey at the penultimate hole had been the result of a “loose 2-iron”, which had almost led to another shot being dropped at the ninth.
But the Scottish No 1 added: “Overall, my game is right there, which is nice to see. A bit disappointing not to come off under par, but I holed a nice one on my last, which is a bonus.”
Russell Knox, the other Scot in the field, sits joint-99th after a 74 that contained a solitary birdie.