NAPA, Calif. — "I don't know if you've ever seen his hands, but they are totally torn up. Every golfer's are ... but he just doesn't stop."

While watching his tee shot on the 17th hole at Silverado Resort, Meghan Koivun was talking about her son, Jackson, the No. 1 amateur in the world and a junior at Auburn University. Jackson was in the midst of carding a second-round 66 at the Procore Championship, good for a share of second-place at 11-under, three strokes behind leader Ben Griffin.

Just last week, Jackson was hoisting the Walker Cup trophy with his U.S. teammates after scoring a team-high three points en route to a 17-9 victory over Team GB&I.

"He's sleeping a lot. We're feeding him a lot," Meghan said jokingly while debriefing the quick turnaround between the two events.

After his first-round 67 at the Procore, Jackson Koivun expressed feeling comfortable at Silverado, a course he'd played before as a junior golfer. It became abundantly clear in Round 2. He navigated the front nine with short birdie putts from 6, 7 and 9 feet on Nos. 1, 4 and 5. A wayward approach led to bogey on the par-4 ninth hole, but he bounced back with a 14-foot birdie putt on No. 10. The highlight of his round was a 270-yard, 3-iron approach into the par-5 12th green, setting up a 2-foot putt for eagle. "All I was trying to do was run something up the front," Koivun said after his round. "It rolled up pretty nice."

The California native added two more back-nine birdies with approaches to 3 and 5 feet on Nos. 13 and 15. He was derailed by a stray tee shot on the par-4 14th hole that flew out of bounds, but managed to limit the damage, hitting the approach shot from his second drive to 6 feet and draining the bogey putt. "I knew I had two par 5s coming in, (so if I) made double on that hole I could make a couple birdies coming in," Koivun said. "Just tried to give myself a look at bogey on 14.

"I was pretty pleased with my iron shots ... a little disappointed in my driver, but still put me in some spots where I could still score from, so can't be too mad about that," said Koivun, who ranked first in Strokes Gained: Approach to Green and T2 in SG: Total in Round 2.

The Procore Championship is Koivun's ninth PGA TOUR start, with his best finish a T5 at the Wyndham Championship in July. He's already clinched his PGA TOUR card via PGA TOUR University Accelerated, but deferred membership in favor of another college golf season. "There's a lot to learn out here," said Koivun on playing in PGA TOUR events. "I'm trying to do it as quickly as I can before I turn pro, whether that's the end of this year, end of next year. Just trying to ... fully understand what goes on inside the ropes."

Meghan Koivun attributes part of this learning process to Russell Henley, who lives 40 minutes from Auburn and frequently plays with Jackson, and other TOUR players who have acted as mentors. Henley also happens to be tied with Koivun at 11-under. "We'll have a little internal match going these next two days," Jackson said.

It's this learning capacity and work ethic that have led to the mental maturity the 20-year-old displays on the biggest stages.

"Jackson likes to come in under the radar," said Meghan Koivun. "He's not one to be showy or anything else. He works really hard, even on Monday, after the Walker Cup, he was out here practicing. That's how he's built.

"It's kind of emotional," she continued. "He's done a lot of growing in the past few years. He's transformed a lot this summer."

Let the transformation continue.