LOUISVILLE, Ky. — Rory McIlroy, with the specter of his recently revealed divorce in progress, did not show a lot of signs of stress in Thursday’s opening round of the PGA Championship at Valhalla.

McIlroy shot a 5-under 66 and, among the morning wave of tee times, stands four shots behind leader Xander Schauffele.

McIlroy shot a 5-under-par 66 and, among the morning wave of tee times, stands four shots behind leader Xander Schauffele.

There already was a massive amount of attention on McIlroy, the No. 2 ranked player in the world, based on the fact he’s returning to the site of his last major championship victory.

McIlroy won the 2014 PGA at Valhalla.

He’s also been heavily in the news with his involvement in the PGA Tour battle with LIV Golf.

And he was coming off a resounding victory at the Wells Fargo Championship, which has become his personal playground.

If that wasn’t enough attention and scrutiny, then came Monday, when news broke that McIlroy had filed for divorce from Eric Stoll, his wife of seven years and the mother of his daughter.

Asked after Thursday’s round how it felt to get back “inside the ropes and just concentrate on golf [with] obviously other things going on this week,’’ McIlroy said, “It’s always nice to be inside the ropes.’’

Asked a follow-up question about “compartmentalizing’’ off-course issues and on-course work, McIlroy was equally as terse when he repeated, “Happy to be here.’’

He called his first round “scrappy for the most part,’’ adding how pleased he was to shoot a low score in spite of it.

“I thought I got a lot out of my game today,’’ McIlroy said. “Some good up-and-downs, [a] chip-in on 6. I’m not really happy with how I played, but at least happy with the score.’’

McIlroy bogeyed the 17th hole, his eighth hole of the day because he started on No. 10, and then got himself into trouble on the par-5 18th when he thought he hit his tee shot into the water.

“I was pretty sure it was in the water, and then when I got up there, I guess the two ball-spotters or marshals said they didn’t really see it or couldn’t really hear it,’’ he said. “I went over to the other side just to check, but was pretty sure it was in the water [and] dropped and took my medicine.

“[I] made a great up-and-down from about 120 yards to make par, which was important after making bogey on 17. That kept any momentum that I had going into the next nine.’’

McIlroy made the turn in 1-under 35 and closed with a 4-under 31 on the front nine, his back for the round.

“It was huge,’’ McIlroy said of the par save on 18. “I could have easily bogeyed 18 and been back to even par.’’