In the eight years since he last won a major, Rory McIlroy has developed something of a routine: he'll shoot himself out of the competition early, then, with the pressure off, he'll backdoor his way into a top-10 finish. It looks impressive in retrospect — McIlroy has totaled 14 top-10 major finishes in the seven-plus years since his 2014 Valhalla triumph — but in the moment, virtually every McIlroy Sunday charge comes with a heavy dose of what-if. What if he'd played like this on Thursday?

This week might just have the answer. McIlroy torched the PGA Championship at Southern Hills with a seven-birdie, five-under performance that posted him atop the leaderboard into the evening on Thursday. The drives carved up the clogged Southern Hills fairways, the putts rolled in from three counties away. Everything clicked for McIlroy in a way that hasn't happened in a major in many years. Thursday marked his best opening round at a major since the 2011 U.S. Open, a tournament he won.

"It was a great start to the tournament. I've been playing well coming in here," he said after his round. "I think when your game is feeling like that, it's just a matter of going out there and really sticking to your game plan, executing as well as you possibly can, and just sort of staying in your own little world. I did that really well [Thursday]. It was nice to get off to that good start and sort of keep it going."

At this year's Masters, McIlroy posted fair-to-middling 73s to start the tournament, and then went 71-64 on the weekend, a furious charge that put him within sight of winner Scottie Scheffler. It was an all-too-familiar shoulda-coulda-woulda scenario for McIlroy, who's been stuck on four majors since winning that PGA Championship, his second, in 2014.

Over the last eight years, the first round has often submarined McIlroy's major chances before they even got started; he's averaged 2.5 strokes per round worse on Thursdays than the other three rounds. Earlier in the week, he acknowledged that in the majors he won, he got off to hot starts.

"You can't plan on getting out ahead. That's just something that happens if you play well and you get some momentum. You're sort of feeling it," he said. "It's not as if I went out with the mindset those four tournaments of I'm going to go out and shoot 65 the first two days and let them all come and catch me. It just sort of happened."

Related: he shot a 65 on Thursday.

McIlroy was grouped with Tiger Woods and Jordan Spieth in one of the most anticipated major-championship tee times in recent history. Crowds surged 20 deep around the trio, but for McIlroy, this was nothing new ... and not a problem.

"It's different playing with him here than it is say at East Lake, because East Lake feels so claustrophobic, the crowds are so much more on top of you," McIlroy said, and he would know ... he was paired with Woods at the 2018 Tour Championship for Woods' landmark comeback win.

The crowds stayed on the far side of the ropes this time around. Spieth didn't give them much to cheer about, finishing at an unremarkable +2, and Woods, after a hot start, cooled off to finish at +4. McIlroy will join them on the tee Friday afternoon at 2:36 p.m. Eastern. He'll try to match his Thursday genius with some Friday brilliance to set himself up for a memorable weekend.

After all, you don't need to play your way into the top 10 on Sunday afternoon if you're already atop the leaderboard on Sunday morning.

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Jay Busbee is a writer for Yahoo Sports. Follow him on Twitter at @jaybusbee or contact him at jay.busbee@yahoo.com.