PORTRUSH, Northern Ireland — As golfers named Brooks, Louis and Shubhankar climbed to the No. 5 tee Thursday at the 148th British Open, two male fans in the grandstand bellowed, “Come on, Ricky!”

“Ricky?” a spectator muttered from just behind the ropes.

Two seconds elapsed.

“Oh, it’s the caddie,” the spectator said. “Took me a second.”

It’s a come-on-Ricky week at Royal Portrush, where caddie Ricky Elliott toils amid surely some of the most on-course caddie recognition in the hushed history of caddies. For one thing, he’s a teammate even more vital than usual in Brooks Koepka’s bid to make his astonishing string of major finishes even more astonishing. In an Open that closed its first round Thursday with Kentuckian J.B. Holmes atop at 5-under-par 66, followed by Irishman Shane Lowry at 4-under 67, Koepka, who has finished 1-2-1-2 in the past four majors, joined at 3-under 68 a horde of 13 that includes Sergio Garcia, Tony Finau and that hip pick, Irish Open winner Jon Rahm.

Koepka did it with his trademark clean brilliance and cocksure strides as the seasoned witnesses from this side of the Atlantic uttered plaudits such as, “He’s some player.” At 29, he also did it alongside a 42-year-old caddie who seems to know a good portion of everybody out there while a good portion of everybody out there seems to know him. That’s because before Elliott caddied these past six years for the guy who has soared to No. 1 in the world, and before Elliott played at the University of Toledo from 1997 to 2000, he grew up in this gorgeous gumdrop of a town and learned highbrow golf on this gorgeous poem of a course.

Whom did Graeme McDowell, the 2010 U.S. Open champion who grew up here, admire as a kid? “Ricky Elliott, who caddies for Brooks Koepka, was a guy I looked up to when I was about 12 or 13 because he was pretty much the best junior player here in Portrush,” McDowell said. “And I eventually followed him to college in America, and that was a big turning point in my life.”

“How many shots did Ricky guide you on?” went a question to Koepka on Thursday.

“Sixty-eight of them,” Koepka deadpanned.

Ricky Week is two-pronged. In prong one, there’s the hometown familiarity. Of the 18 holes Koepka and Elliott walked Thursday, Elliott saw familiar faces on 18 of them, he said. So did his father, a longtime owner of an auto-repair garage who walked the course with them.

“I have lived here a lifetime,” Pat Elliott said during the round.

“Everybody’s got tickets,” Ricky Elliott said after the round, “and excited that the Open’s here, and, yeah, they’re all enjoying the experience.”

“It is an experience,” Pat Elliott said. “There’s no doubt. It’s been nice to have it here, the Open.”

“Ah, it was all right,” Ricky Elliott said, “just a few showers in between a bit of sunshine, you know. At least it didn’t last too long. It was warm enough.”

That last quotation, devoid of any of the emotion that might have laced the day, hints at the second prong: Elliott’s curious role in Koepka’s stunning pursuit of a fifth major title. “I don’t have to learn much,” Koepka said. “My caddie knows it all. I’m OK with not knowing much.” And: “It’s easy when he’s just standing on the tee telling you, ‘You have to hit it in this spot,’ and I just listen to him. I don’t have to think much. I don’t have to do anything.”

As Elliott said of the Portrush shots, “I’ve seen them all.”

Around they went, together yet again, if more meaningfully, and even through the sporadic deluges like the one on the No. 2 tee, of which Koepka said, “Man, I felt like the world was going to end.” (True to unshakable form, he actually prefers the rain; it makes things more challenging.)

Koepka, winner of the U.S. Open in 2017 and 2018, victor of the PGA Championship in 2018 and 2019 and runner-up at the 2019 Masters and U.S. Open, drew from his big bushel of skills. The short game he has noted as strongly upgraded over recent years coaxed the oohs and aahs: a chip on No. 5, a chip on No. 10, a putt curving flawlessly on No. 14.

Further, were there a museum of excellent lag putts, he could have qualified for a few exhibits. “He keeps it light,” Koepka had said of Elliott. “He knows not to talk about golf while we’re out there. He knows if I’m getting a little bit tense, maybe upset, angry, whatever it is, he can tell just by my walk.”

One of the crests of their tandem came at Shinnecock at the 2018 U.S. Open, where Koepka felt lost at 7 over after 25 holes, and Elliott reminded him he wasn’t (lost), and Koepka wondered what Elliott meant, and Elliott said, “You’re not far out of it,” and Koepka used that propulsion to get going, and Koepka won.

They started in mid-2013 after a recommendation from Claude Harmon, Koepka’s swing coach, and a 30-minute phone call featuring Elliott’s lightness. They teamed at the 2013 PGA Championship, including on Sunday in the grand test of a pairing with Tiger Woods. “I think the way he went about things was different from any caddie I’d ever had,” Koepka said. “The confidence behind what he thought the club might be, the wind direction or what the yardage was, he was dead sure in it. He just knew the right things to say, and I think that’s what makes a great caddie. ... And the way he went about that I thought was super impressive. And that’s kind of when I was like, ‘All right, this is my guy.’ And then hopefully he doesn’t leave me. But he’s not going to leave me for a long time.”

They reached the 18th fairway Thursday with only one bogey (on No. 17) on the card, the most important team in the game at the moment. A spectator who seemed to know Elliott boomed, “Night comes early in the morning, Ricky!” Whatever the frolicsome sentiment there, the team was laughing in the fairway. Their comfort with their mission here might yet decide this event, and it called to mind something Woods said Tuesday.

“Tell you a funny story,” said Woods, who shot a dismal 78. “I texted Brooksie, ‘Congratulations on another great finish.’ What he’s done the last four major championships has just been unbelievable — to be so consistent, so solid. He’s been in contention to win each and every major championship. And I said, ‘Hey, dude, do you mind if I tag along and play a practice round?’ “

Woods paused, then stoked laughter when he added, “I’ve heard nothing.”