NEWTOWN SQUARE, Pa. — It’s a packed house at the PGA Championship. There are 33 players within two strokes of the lead, setting up some theatrics for Friday and onward. Aronimink Golf Club delivered in its return to professional golf, defying the expectations of many who expected it to be a shootout. Instead, the golf world was treated to a stern test as gusty conditions, tough pin locations and firm greens forced players to bring their very best.

Concerns of heavy rain overnight were largely avoided, with only a quarter-inch falling in the Philadelphia area ahead of Thursday’s first round. That seems to allow the course to play exactly how the PGA of America intended this week, fair but firm.

Scottie Scheffler is the headliner after 18 holes. He co-leads a crowded pack at 3-under. Of the big four favorites entering the tournament – Scheffler, Rory McIlroy, Cameron Young and Matt Fitzpatrick – Scheffler is the only one under par.

McIlroy was the biggest disappointment of the bunch. He shot 4-over 74 as he struggled mightily with his driver. Typically, his superpower, McIlroy hit only five fairways, which put him on the defensive the whole round. He scrambled well on the front nine but couldn’t keep it up on the back nine. He made four straight bogeys to end his round.

What else did you miss from the first round? We tracked everything as it was happening. Re-live the top moments by reading below.

5:29 p.m. ET: Here comes Scottie Scheffler. He started slow, 1-over after four holes, but he’s quickly asserted control over this golf tournament. The reigning PGA Championship winner birdied the sixth, seventh, 10th and 11th holes to tie the lead at 3-under.

Is this tournament already in Scheffler’s hands?

5:25 p.m.: Corey Conners is putting together an insane ball-striking round right now. If only the putter would cooperate.

Currently co-leading at 3-under, Conners leads the field in average proximity to the hole. That also means he's missed birdie putts of six, nine, 10, 13 and 14 feet.

4:19 p.m.: As the afternoon groups settle into their rounds, the truth about Aronimink Golf Club has been revealed: It's tough out here.

It's windy, chilly, the rough is sticky and the greens are slick. Initial predictions of a drag race to 20-under have been declared all but dead on arrival.

Aldrich Potgieter's 3-under remains the mark to beat with a few others in the club, but the scoring average sits a good two shots over par as we enter the late stretch of this opening round.

Justin Thomas has the best chance to set a new mark. His driver has been on point on Thursday, with his short game rescuing him from any trouble encountered with his approach play. This included an up and down from on the green on No. 7.

Thomas reached 3-under with a gorgeous tee-shot to six feet at the difficult par-3 eighth, only the fifth birdie on that hole today. He goes out in 32.

Scottie Scheffler reached red numbers with back-to-back birdies on Nos. 6-7 after an early blemish, and will look to hang on and develop a rhythm heading to the more difficult back nine.

2:15 p.m.: Fresh off the acquisition of his second green jacket, Rory McIlroy struggles to a 4-over 74 opening round. McIlroy, who dealt with foot discomfort earlier in the week, made five bogeys in his final six holes, in large part due to an erratic driver and cold putter, to card a 4-over 74. Per Justin Ray, the last player to shoot an opening-round 74 at the PGA Championship and go on to win was Payne Stewart in 1989.

"Yeah, I'm just not driving the ball well enough," said McIlroy after the round. "It's been a problem all year for the most part ... Like I miss it right, and then I want to try to correct it. And then I'll overdo it, and I'll miss it left. It's a little bit of back-and-forth that way. So that's pretty frustrating, especially when like I pride myself on driving the ball well."

I just need to try to figure it out. I honestly thought I'd figured it out. Just sort of, once I get under the gun, it just seems like it starts to go a little bit wayward on me."

More on McIlroy's round here.

Meanwhile, three-time PGA Championship winner Brooks Koepka posts a steady 1-under 69. Koepka hit 15 Greens in Regulation and was second in Strokes Gained: Approach.

Another PGA winner, Xander Schauffele, does one better with a 2-under 68. "It's always nervy playing in a major, so nice to get off to a good start for sure," Schauffele said. "It's Thursday. You're just trying to get in a decent position and kind of feel out how you're playing."

1:44 p.m.: After taking a share of the lead, Jordan Spieth gives two bogeys right back to the field on holes No. 16 and 17. The Spieth Experience remains consistent and relentless.

1:20 p.m.:Jordan Spieth has officially tied the lead at the PGA Championship.

Yes, it's barely the afternoon of the first round. Yes, he isn't even in the house yet. But it's hard to contemplate the situation that could develop if Spieth can be a serious factor this week, given his popularity. Spieth has recently elevated his game off the tee, and has been using that to his advantage through 15 holes here in the opening round, reaching 3-under.

Meanwhile, the Garrick Higgo snafu continues to unfold. Higgo was able to bounce back to a 69, including his two-stroke penalty for being late.

"I was there on time, but the rule is, if you're one second late, you're late," Higgo said. "So if you think about it, I was there on time.” More on that here.

12:01 p.m.: One of the first players to post a score Thursday was Aldrich Potgieter. The young South African, famously known as being the longest driver on the PGA TOUR, opened with a 3-under 67 in a potential canary-in-the-coal-mine signal for those claiming Aronimink rewards brute force off the tee.

However, Potgieter’s game has evolved considerably in recent weeks. At the RBC Heritage, he carded three consecutive rounds of 67 around the notably tight corridors of Harbour Town Golf Links. While a Sunday 75 dropped him back to a T25 finish, his ability to navigate a course of that style showed the young bomber may be developing some sidearms to complement his primary weapon.

"I'm probably hitting around 10 or 11 (drivers) at least out there," Potgieter said post-round. "It's definitely wind and tee box dependent."

With favorable conditions expected and both temperatures and winds projected to increase as the week progresses, Potgieter’s opening 3-under should do little to discourage expectations for what still shapes up as a formidable major championship test in Pennsylvania.

11:29 a.m.: The morning wave is in full flight, with the marquee groups now making the turn. One interesting note: most of the big names started on Aronimink’s back nine, which is the decidedly harder side of the golf course. It’s a small sample, but the front nine is playing nearly a stroke easier than the back nine.

So here’s where a few of the big names stand midway through the round:

• Rory McIlroy (even): A very ho-hum start for McIlroy, who opened with a bogey on the 10th but got it right back at the 11th. He failed to capitalize on the lone par 5 of the back nine, the 16th, hitting a mediocre greenside bunker shot. Still, nobody is going low yet, so a few birdies on the easier front nine could have McIlroy in the mix quickly.
• Xander Schauffele (2-under): A solid start from a player who needs to start contending in majors again. He birdied three of his first four holes. He dropped a couple from there, but looks sound off the tee and crucially on the greens, which is where he has struggled recently.
• Brooks Koepka (1-under): There’s something about Koepka and PGA Championships. He fits their modern ethos, hitting drivers straight and long with a really solid approach game. He fought off an early bogey at the 10th and grabbed birdies at 12 and 14, two of the hardest holes thus far.

11:02 a.m.: The 11th hole is one to watch all week. It’s already delivering this morning. The relatively short par-4 boasts the wildest green complex on the property and will be the site of theatrics, good and bad.

Dan Brown just holed out for eagle, spinning one off a big slope and finding the cup. The hole has yielded quite a few birdies, almost all of which have come while putting below the hole. The green pitches severely from back to front, so any approach shot that misses long leaves a treacherous putt. That was on display as Bryson DeChambeau came through. He left his ball in the fringe just long of the green. He aimed perpendicular to the hole and barely tapped his putt, but it still raced 60 feet past the hole.

It was a prime example of the volatility of that particular hole. It can be easy if you leave yourself in the right spot. If you don’t, disaster is lurking. It was even the subject of some concern among players earlier this week, who worried that the green could become too penal. PGA of America's Chief Championships Officer, Kerry Haigh, said they are closely monitoring that hole.

"The hole location has to be determined based on the speed of the green," Haigh said. "The green is a slower speed today than the other greens and has been all week."

9:32 a.m.: We've had our first quirk of this major championship unfold already.

Garrick Higgo received a two-stroke penalty for arriving late to his Round 1 tee time. More on the situation here.

Here’s a few of the marquee tee times to watch for on Thursday:

• Ludvig Åberg, Rickie Fowler and Bryson Dechambeau (8:18 a.m. ET)
• Xander Schauffele, Brooks Koepka and Tyrrell Hatton (8:29 a.m. ET)
• Rory McIlroy, Jordan Spieth and Jon Rahm (8:40 a.m. ET)
• Viktor Hovland, Collin Morikawa and Shane Lowry (1:32 p.m. ET)
• Tommy Fleetwood, Chris Gotterup and Robert MacIntyre (1:43 p.m. ET)
• Cameron Young, Keegan Bradley and Justin Thomas (1:54 p.m. ET)
• Scottie Scheffler, Matt Fitzpatrick and Justin Rose (2:05 p.m. ET)

This PGA Championship is, in many ways, a blank canvas. Aronimink is a relatively unknown venue, with little familiarity of the course, how it will play and who it will favor. The field is wide open. The top players – like Scheffler, McIlroy, Young and Fitzpatrick – are playing great, setting up expectations of a high-drama affair.

Simply: it’s an exciting week with tons of possibilities. We’ll have you covered with updates throughout Thursday’s opening round.