Three things from Mason Andersen, who will be a freshman at ASU this fall as he prepares for the U.S. Open. Andrew Vailliencourt/azcentral sports

Editor’s note: Here is an update after Mason Anderson’s first round Thursday at the U.S. Open:

ERIN, Wis. – Mason Andersen was warned.

Jon Rahm, the world’s 10th-ranked player and a former standout at Arizona State, told the 18-year-old Andersen during a Monday practice round at Erin Hills that the incoming Sun Devil was going to be “terrified” when he stepped on the first tee in his first U.S. Open on Thursday afternoon.

The advice? “Grip the club soft and hit it as hard as you can,” Rahm told him.

The result? “I just crushed my drive,” Andersen said.

With Andersen playing in one of the day’s final groups, the grandstands were nearly empty, but there were still nerves for the Chandler native, one of 14 amateurs in the field this week. But not for long.

With his dad, Rick, on the bag, Andersen made three birdies en route to an opening 1-over 73, which has him tied for 61st after 18 holes. He’s eight shots off of Rickie Fowler’s lead, but he beat world No. 1 Dustin Johnson by two shots, No. 2 Rory McIlroy by five and No. 3 Jason Day by six.

“That’s exciting,” Andersen said. “I played good, I hit the ball good, but there were a couple holes where I just made mental errors. 73, I probably would’ve taken it before the round. But after the round, knowing how I played, honestly I probably easily should’ve shot a 70, at least.”

Tough critics those teenagers. Andersen really only had one trouble stretch, making bogey on No. 11 and double on No. 12 after just finding the rough off both tees. He also failed to capitalize on deep drives on Nos. 1 and 18, making par.

Overall, though, Andersen was proud of how he handled himself in his first major-championship round. And he’s confident going into his morning round on Friday.

“I’m just going to go into tomorrow and expect something under par,” Andersen said. “That should do the trick and get me into the weekend.”

At 18 years old, that would be quite the accomplishment.

Once in awe, now Arizona teen is amazed to be at U.S. Open with his ASU role model

ERIN, Wis. – When Mason Andersen took his unofficial visit to Arizona State, he didn’t get to meet Jon Rahm, but he remembered seeing the former All-American hitting balls on the range and being in awe.

That day, Andersen “tried to just stay out of his way.” But on Monday at Erin Hills, Andersen found himself teeing it up in a practice round alongside Rahm, now a PGA Tour winner and the world’s 10th-ranked player.

“It was amazing,” said Andersen, 18, who will make his first major start at this week’s U.S. Open. “He’s such a great guy, and he had so much advice for me, too. Just to talk to him and pick his brain; I can see why he’s at the top of leaderboards week in and week out.”

Andersen, a Chandler native who will begin college at ASU this fall, hopes to one day be just like Rahm, playing on the PGA Tour. Their games are already similar. Rahm’s agent and former Sun Devils coach, Tim Mickelson, recruited Andersen and said Andersen, like Rahm, doesn’t have any glaring weaknesses.

Andersen’s coach at Hamilton High School, Steve Kanner, agrees.

“He is a complete player who is able to overpower most golf courses,” Kanner told azcentral sports.

RELATED: U.S. Open opportunity “overwhelming” for incoming Arizona State golfer Mason Andersen

Overpowering 7,741-yard Erin Hills, though, may be difficult for the young amateur. Instead, Andersen plans on taking advantage of the greens – he said his speed control has been great so far this week – and playing like he did when he sectional-qualified for the U.S. Open last week in Newport Beach, Calif.

“Sectionals taught me a lot,” Andersen said. “I just stayed out of my own way. … It was a really stress-free round of golf that first round. It felt like a 72 but it was a 64. I just let things happen. Especially on this course, you have to stay patient.”

Staying patient was one of the things Rahm stressed to Andersen.

“I told him, listen, this is a marathon,” Rahm said. “It’s going to be mentally exhausting. It’s going to be a long week. Take it easy. … Don’t play 18 holes every day because you’re going to run out of steam when you get to Thursday.”

It will surely be a whirlwind week for Andersen. His dad, Rick, will caddie. A large group of family – including Andersen’s sister, Abby, an ASU softball commit – and friends are in Wisconsin, too, as is Andersen’s swing coach of more than two years, Ben Weir.

And then there’s the hundreds of fans who could be surrounding the first tee when Andersen tees off Thursday afternoon.

Andersen admits he’s nervous. He told Rahm that on Monday.

“It’s the atmosphere that gets me and I asked him, ‘What do you do?’” Andersen said. “He’s like, ‘You know what? Don’t worry about those people. Just do your thing and block it all out.”

Rahm’s advice to Andersen on that first tee shot?

“I was like, ‘You know, Mason, you get to that first tee, you’re going to be absolutely terrified … it’s going to be the scariest thing you’ve ever faced,’” Rahm said. “I told him to grip the club soft and hit it as hard as you can.”

Luckily for Andersen, that first hole at Erin Hills is a par 5.