Rory McIlroy had one singular thought in his mind entering the U.S. Open first round Thursday at Shinnecock Hills: Don’t do what he did in 2018, the last time the Open was played at Shinnecock.

McIlroy opened with a 10-over-par 80 in 2018 and shot himself out of the tournament en route to missing the cut.

On Thursday morning, McIlroy was actually cruising through his first round … as much as anyone can cruise around Shinnecock in U.S. Open conditions with 30-mph winds.

The 37-year-old from Northern Ireland, back-to-back winner of the Masters and ranked No. 2 in the world, was 3-under par with two holes to play.

And then … well, Shinnecock. He bogeyed his final two holes to drop to 1-under, but still walked away satisfied with his day’s work, one shot off the lead after the morning wave of tee times were complete.

“It was a day to really just keep yourself in the tournament and not shoot yourself out of it, which is exactly what I did eight years ago here,’’ McIlroy said after shooting 69. “So (I) sort of went out with the mindset that pars were going to be good, and if you could pick up a couple of birdies here and there, that’s always a bonus. But really just minimizing the mistakes. I did that for the most part today.

“With the conditions today, anything under par or anything around even par is a good score.’’

He called the conditions “so tough, so difficult,’’ adding, “I didn’t feel like I hit two bad iron shots on the last two holes [Nos. 8 and 9] and put myself in pretty difficult spots and wasn’t able to get it up-and-down. But overall, a really good day.’’

McIlroy pointed to the 2018 U.S. Open at Shinnecock as a turning point to how he played U.S. Opens, and the results show his improvement.

Though he won the 2011 U.S. Open, McIlroy missed the cut in the tournament four times from 2012 to 2018.

Since 2019, his worst finish in a U.S. Open was a tie for 19th last year. Other than that, he has no finish lower than a tie for ninth, and he finished runner-up twice.

“The big thing was I needed to change my mindset,’’ McIlroy said of his play at U.S. Opens. “I played those two days in 2018, and then I got to the Travelers [Championship] the next week [and] I remember feeling so much in my comfort zone going to TPC River Highlands and thinking to myself, ‘I’ve got this backwards. I should be in my comfort zone at Shinnecock and not here.’

 “I remember flying back from Dubai at the end of 2018, and I would keep a journal or a diary. I wrote in it that, from 2019 going forward, I’m going to build my game to compete at the major championships and excel at the toughest tests that we have. 

“Working on the things that you need to do well to excel at these, which is flighting the ball, hitting your numbers, wedge play, short game, putting. [That] is all the stuff that I feel like I’ve improved over the last few years.’’

The highlight of McIlroy’s round on Thursday came on the par-5 fifth hole, which was his 14th of the round, having started on No. 10.

“Driver, pitching wedge, putt,’’ McIlroy said. “I think I had 194 (yards) to the pin. I was trying to pitch the ball like 180, and I ended up pitching the ball like 190. I carried that pitching wedge 190 yards. It just shows how strong the wind is out there.

“It’s nice to have a wedge in your hand with second shots at par-5, and with the greens still being receptive, I could get the ball to stop on that green. Yeah, it was nice to hole the putt.’’