ORLANDO, Fla. (AP) — Daniel Berger has enough history at Bay Hill Club & Lodge to know what kind of test to expect. He made nine birdies, all but one of them inside 10 feet, for a 9-under 63 and a round no one was expecting Thursday in the Arnold Palmer Invitational presented by Mastercard.

Berger posted his bogey-free round in the morning and by the end of the day, he had a three-shot lead and a score that was nearly nine shots better than the average of the 72-man field.

Collin Morikawa had a finish he could have used last year when he was runner-up. He was middle of the pack until closing eagle-birdie-birdie for a 66. He was tied with Ludvig Åberg, whose round should be considered as impressive as what Berger did.

Åberg played in the afternoon when the greens looked more yellow, the wind began to gust and swirl, and storm clouds gathered without really threatening. He hit a 5-iron to 25 feet for eagle on the par-5 12th and shot 66, three shots better than anyone who played late.

Scottie Scheffler played in the mid-morning and shot 70, his first opening round under par since his first tournament of the year (which he won). Rory McIlroy played late and was slowed by a shot off the rocks and into the water on the 13th for double bogey, and a bogey on the 18th for a 72.

Bay Hill often gets referred to as a mini-U.S. Open because the greens are firm – McIlroy hit a shot into the par-3 14th that bounced like it hit a trampoline – and the rough is thick. Russell Henley had one lie in which he had to stand directly over the ball to see about eight dimples.

Berger's U.S. Open reference was different. He compared it to the 66 he shot in the third round at Shinnecock Hills in 2018 when he played early and went from 11 shots back to a tie for the lead.

“It has that U.S. Open kind of feel to it,” Berger said. “I think the course is just going to get tougher as the week goes on. The greens are going to get firmer. ... So yeah, just hit it in the fairway and try to make as many putts as you can.”

Cameron Young had seven birdies in his round of 67. He also played in the morning. Another shot behind was a group that included Adam Scott and Xander Schauffele.

“It’s a little bit like a mini U.S. Open playing Bay Hill,” Scott said. "You can shoot your way out of it on the first round because the score can get away from you. So if you’re 5 over today, it’s a long way back – especially when there was a 9 under out there, which is hard to see.

“Nice to not shoot my way out of it.”

Åberg was going along nicely with four birdies on the front, when he began the back nine with back-to-back bogeys. “Not ideal, but also knowing that bogeys might happen at Bay Hill when it’s tricky,” he said.

That's what made the eagle on the next hole so important.

He also was along for the wild ride of Cognizant Classic in The Palm Beaches winner Nico Echavarria, who went out in 30 and looked like he might catch Berger. But the Colombian shot 42 on the back, including a triple bogey on the 12th hole when from 44 yards it took him three shots to get to the green, and from 6 feet it took three putts to get in the hole.

At the end of the day, only 32 players broke par. That included Daniel Bennett of South Africa, who plays at Texas and received the Arnold Palmer Cup exemption.

Justin Thomas had a rude welcome back from five months away recovering from back surgery. He had a double bogey on the par-4 11th when he missed the fairway and missed a 3-foot putt, and another double on the 16th when a wedge from 81 yards went into the creek in front of the green (it actually bounced into the creek). He shot 79 and needs a low score Friday to make the cut.

“It was kind of hard to say it was good to be back out,” Thomas said. “Yeah, not obviously how I expected it to go. But the rust aspect kind of unfortunately was a little bit of what I anticipated.”