The 19-year-old has never really seen anything like this before, but Kim's caddie, LaRue Temple, has seen it plenty of times.
"This is Merion," Temple said. "Merion stands up."
Temple, who has caddied at the course for 16 years, wasn't planning to work the tournament. There aren't many opportunities for local caddies at a major event, and he turned down the offer to work in the bag room or drive a cart in favor of buying tickets and attending as a spectator. He was at the course Monday to watch the practice round when he felt a tap on his shoulder, and the caddiemaster asked if he wanted to get on a bag.
"It was just right place, right time. There's a lot of qualified caddies here at Merion. I don't want to make it like I was picked or chosen. Kim needed a caddie, and they saw me in the parking lot," Temple said. "They told me he's a great golfer and plays for the Cal team and they won a lot. I just said, 'Cool.' "
Only a handful of regular Merion caddies are actually carrying bags this week. The pros bring their own or know someone from the region. Temple, 30, originally from North Philadelphia and a graduate of Olney High School, says things like this just happen to him.
"It's cool to represent the course. This place has meant a lot to me for a long time," Temple said. "It was special, hearing my name yelled out. Mike's like: 'Wow, you're getting more cheers than me.' "
The course represented itself very well again on Saturday. Mickelson was the only player under par for the tournament and there were seven players bunched within 2 shots of one another at the top of the leader board. Kim is in 10th place, which represents a nice payday, except he's an amateur and isn't going to get paid. That's probably something that occurred to Temple, too, but he's just enjoying the ride.
"We didn't even talk about money," he said. "I have no clue what I'm getting for this or anything."
Regardless, Kim is getting the benefit of thousands of rounds of experience from Temple. Even veteran players are having plenty of trouble with Merion's demanding shots and tricky greens. The members and regular caddies aren't surprised.
"There are some nasty pin placements, but we see these every day," Temple said. "I'm just doing what he asks me to do. If he wants me to read a putt, I'll read the putt. If not, I get out of the way. There are certain shots where I might think he's being a little too aggressive, and I'll say: 'You sure you want to do that?' "
Kim was rolling along until he snap-hooked a 3-wood off the 16th tee, and the final three holes came apart on him. He will try to get it back together for the final round and maybe even start that what-if stuff again.
He's already been pretty resilient this month. Kim finished tied for 49th at the NCAA championships, then two days later qualified for the Open with a combined 13 under during a grueling 36-hole sectional tournament.
"I've been pretty excited ever since I qualified," Kim said. "I came in here with not too many expectations, and I'm just trying to keep it that way."
LaRue Temple didn't have any expectations for the week, either, aside from coming out to the course and watching the tournament. Now, in a very real way, he's in the tournament.
"The joke among the caddies is that when people are playing slow and grinding out every shot, you say, 'Come on, dude. This isn't the U.S. Open.' Now, it is the U.S. Open," Temple said. "But I still see the same faces. I see the caddies spectating. I thought I'd be more nervous. But it's like the Member-Guest, just with a lot more people watching."
A lot more. Temple feels lucky just to be a part of the action, but Michael Kim got pretty lucky this week, too.
Contact Bob Ford at firstname.lastname@example.org. Follow @bobfordsports on Twitter.