OAKMONT, Pa. — The first round of the 125th U.S. Open at Oakmont Country Club is in the books, and though one of golf’s toughest tests put several players on their heels Thursday, a handful fought off the course well and headed into Friday with hopes of continuing their strong start.

J.J. Spaun shot a record 31 on his first nine holes of the championship and then held on for his next nine to card a formidable, bogey-free 66 to take the first-round lead. Only nine players behind Spaun are under par.

With 54 holes left, here’s what caught our eye Thursday and what we’re watching for in the second round.

What did you see in Round 1, and how do you expect Oakmont to play the rest of the week?

Mark Schlabach: There was plenty of carnage at Oakmont on Thursday, which makes Spaun’s 4-under 66 that more impressive. As two-time major champion Xander Schauffele said after his opening round, it’s only Thursday, so good luck keeping that up over the next 54 holes.

It seemed that once a golfer’s round started going the wrong way, especially on the front nine, it was difficult to get things going back in the right direction. The par-5 fourth (4.91) and the 17th (3.93), the shortest par-4 at 327 yards, were the only holes with average scores under par. The 463-yard ninth, the longest par-4, was the most difficult (4.54).

It was hot Thursday, so the course dried up in the afternoon. Temperatures are forecast to be back in the low 80s Friday, so conditions might be difficult again. There’s a decent chance of thunderstorms Saturday and Sunday, so things might get softer on the weekend.

LIV Golf League captain Jon Rahm, who carded a 1-under 69, said conditions were much different in the afternoon than the morning. The afternoon wave’s average scoring was about one stroke better.

“Some of those holes were playing a little shorter,” Rahm said. “Some of those bounces were maybe slightly firmer.”

Paolo Uggetti: Despite a shocking 4-under round from J.J. Spaun and 10 players finishing under par, Oakmont still had the bite we expected Thursday. Some of the best in the world were humbled by thick rough, deep bunkers and countless awkward lies while a whopping 16 players finished 10-over par or worse. I mean, even the No. 1 player in the world made six bogeys — the second-worst mark of his career.

All of this, of course, after the course was soaked with ample amounts of rain over the past week.

“The easiest we’re going to play this golf course is today,” Patrick Reed said. “Even though the wind was kind of switching around, when I was watching it earlier on the coverage, guys were spinning balls back up the hills on 1 and 10. That’s never going to happen again.”

“It’s still not as firm as a typical U.S. Open probably is,” Brooks Koepka said. “I mean, I understand there was rain on Sunday night, so I get it, but it’s still — it’s going to have some heat to it this weekend.”

The heat is coming. Thursday is probably the easiest the course will play from a setup standpoint, and if the current forecast of more rain on the weekend holds, it wouldn’t shock me to see the USGA gets a little bit meaner with some of the pin positions and green speeds.

“You shoot four level-par rounds, you’re walking away with a medal and a trophy,” Bob MacIntyre said. “I’m sure I’d take that.”

Though I’m not sure MacIntyre is right about that, if anyone else can replicate Spaun’s 66 the rest of the way, they’ll likely be in a great spot to win the year’s third major.

Who has work to do Friday to be around for the weekend?

Schlabach: Oakmont chewed up plenty of superstars Thursday: world No. 1 Scottie Scheffler (3 over), Bryson DeChambeau (3 over), Masters winner Rory McIlroy (4 over), Patrick Cantlay (6 over), Justin Thomas (6 over), Justin Rose (7 over), Sepp Straka (8 over) and Shane Lowry (9 over). Scheffler, DeChambeau and McIlroy might still be within striking distance, but the others have plenty of work to do if they’re going to be around for the weekend.

“I think the rough is incredibly penalizing,” DeChambeau said. “Even for a guy like me, I can’t get out of it some of the time, depending on the lie. It was tough. It was a brutal test of golf. But one that I’m excited for tomorrow. If I just tidy up a couple things and get some momentum going my way, we’ll see where it goes.”

The top 60 scores and ties will make the 36-hole cut, and if Friday’s play is anything like the opening round, the cut line is going to be several strokes over par. There were 78 golfers at 4 over or better after 18 holes, and the cut line is probably going to climb higher.

Who do you think is the favorite now after Round 1?

Schlabach: I’ll go with Brooks Koepka, and I’ll admit I was beginning to wonder if his days of contending at majors were over. He missed the cut at the Masters and the PGA Championship, and didn’t look very good doing it.

Koepka’s results haven’t been much better in the LIV Golf League; he tied for 33rd at 3 under in last week’s event in Gainesville, Virginia.

But the five-time major champion posted a 2-under 68 and is just two back of Spaun. He made an eagle on the par-5 fourth and birdies on Nos. 17 and 18 to take momentum back to his rental house.

“I thought I played pretty consistently, drove it really well,” Koepka said. “Iron play was pretty good. When I did miss it, I felt like I missed it in the correct spots. A couple of good bunker shots. I missed one little short [putt] on 14 maybe. Other than that, I thought I played very solid. I’m really happy with the way I finished, and hopefully it leads into tomorrow.”

Koepka hit only six of 14 fairways but gained nearly three strokes around the greens and almost 1½ off the tee and on the greens.

He said he has been working through bad swing positions and poor habits for months. He got a good scolding from swing coach Pete Cowen in a bunker during a practice round Monday. Koepka said Cowen ripped into him so badly that Justin Thomas had to check on him.

“Yeah, Pete, I’ll keep that between us,” Koepka said. “I wasn’t happy with it, but it was something I think you need to hear, or I needed to hear, at the right time. It’s not the first time he’s done it. He’s not afraid to.”

Uggetti: Before the tournament, I picked Rahm to win his second U.S. Open, and I think he remains a true favorite after spinning around Oakmont in a pretty tidy 69 strokes Thursday. This is actually the sixth straight U.S. Open appearance where Rahm has kicked off the tournament with a 69.

“I’m extremely happy,” Rahm said. “I played some incredible golf to shoot 1-under, which we don’t usually say, right?”

Rahm gained 3.55 strokes off the tee during his opening round, which tops all other 155 players. The driver, he said earlier this week, had been giving him trouble going back to last year, and he has made a couple of equipment changes and tweaks, including a new shaft, that have clearly helped. He hit 10 of 14 fairways Thursday, well above the field average, and is also top five in strokes gained: approach.

Data Golf currently gives Rahm a 15.3% chance of winning the tournament — the highest in the field — and if his putter even just slightly improves (he lost about half a shot on the greens), he will be in prime position at a course like Oakmont. So yes, I’m sticking with the Spaniard.

Biggest surprise/biggest disappointment?

Schlabach: What about James Nicholas, who is the 502nd-ranked golfer in the world? It took the 28-year-old several attempts to qualify for the U.S. Open, but he looked like he belonged with a 1-under 69 on Thursday.

Nicholas played one season of football and four of golf at Yale. He was the 2019 Ivy League Player of the Year and spent last season on the DP World Tour. Even better: his grandfather and father worked as orthopedic surgeons for the Jets, Knicks, Islanders and Rangers. Both operated on former New York Jets quarterback Joe Namath’s knees. Maybe Nicholas will guarantee he’s going to make the cut.

There are so many choices for disappointments, but it’s hard to dump on anyone because the course is hard. I thought we’d see better results from JT, who is in danger of missing the cut in his third straight U.S. Open and second consecutive major. He lost more than two strokes in approach, missing nine of 18 fairways, and lost more than a stroke around the greens. He putted well.

Uggetti: The obvious answer is Spaun, but this is a guy who went to a playoff at the Players with Rory McIlroy in March and had a chance to beat him. Even more surprising is Thriston Lawrence at 3-under, who competed at last year’s Open Championship, but missed the cut at this year’s first two majors.

“I feel like it fairly suits me,” Lawrence said of Oakmont. “I like a tough test, and I feel like from the tee, just the distance I hit it, my targets are quite big for the distance I hit it off the tee.”

Lawrence had only one true bad hole Thursday — the par-4 ninth, which he doubled — but aside from that, he kept a clean card and made four birdies. Lawrence gained strokes on the field in every category, but much like Spaun, it was the putter (3.53 strokes gained) that propelled him to a strong round. We shall see if that holds up.

As far as true disappointments go, it’s easy to look at McIlroy, DeChambeau and Scheffler, even though their rounds don’t put them out of it just yet. A 5-over from a player like Joaquín Niemann stands out if only because he continues to struggle at major championship first rounds and has yet to truly compete despite winning four events on LIV this year.

Neither of those players however shot themselves out of the tournament like Shane Lowry did. The Irishman finished at 9-over despite holing out for eagle on the third hole. In other words: It could have been even worse. Lowry contended the last time the U.S. Open was at Oakmont in 2016, but this year he’ll have to hope for a Friday miracle if he wants any shot at playing the weekend.