Oahu Country Club can be many things.

Challenging. Unforgiving. Humbling.

Add the pressure of playing in the Manoa Cup — arguably the most prestigious amateur golf event in the state — and the 6,041-yard course can quickly go from friend to foe. It depends on the mind-set of the golfers, who after qualifying via stroke play on a Monday, have to adapt to match play on a Tuesday.

Some are better at it than others, including four-time champion Brandan Kop, who closed out his match on 14 in the 110th edition of the event. Seeded second after a birdie-dominated 5-under 66 on Monday, Kop relied on his wedge-and-putter game — and a surprisingly accurate driver — to defeat Larry Goeas 6 and 4.

“This tournament keeps me young,” said the 57-year-old Kop, whose last Cup victory came in 1998. “I like playing with the young guys, I enjoy the one-on-one.

“They say this favors the young guys (golfers don’t use carts), but there’s something about having experience and the mental game for this. You do have to be in shape. It’s the only tournament you have to train for. I’ve said I want to keep playing in it until I’m 60. There is a prestige to it.”

There were 11 upsets (based on seeding) among Tuesday’s 32 men’s opening-round matches, the biggest being seventh-seeded Jacob Torres eliminated by No. 58 Alex Kam (21 holes) and eighth-seeded Aj Teraoka eliminated by No. 57 Kelii Kamelamela-Dudoit (1 up).

All four previous champions — defending champion Andy Okita, Matthew Ma, Tyler Ota and Kop — advanced to today’s second round, as did last year’s runner-up, Evan Kawai.

On the women’s side, the only upset among the 16 matches was No. 4 Heather Carr losing to 13th-seeded Victoria Takai, 4 and 3. Top-seeded Brittany Fan won her match against Katrina Huang, 4 and 3.

Among the more intriguing matches on Tuesday was between first-timers Hunter Hughes and Caleb Ah Mow, won by Hughes 3 and 2. Hughes, a recent University of Hawaii graduate, was a scout team quarterback for the Rainbow Warriors the past two seasons and has been working in the OCC pro shop for the past three months. Ah Mow is a recent graduate of Hanalani Schools and will play for Chaminade this season.

Hughes led after a birdie on No. 2 but was challenged by Ah Mow the entire way. Hughes was 3 up twice, only to have Ah Mow pull to within 1 both times, the last after parring No. 14.

No. 15 proved to be the turning point when Ah Mow sliced his tee shot into the trees, a shot deemed out-of-bounds, giving him a one-shot penalty and having him play a second tee shot as his third stroke. Hughes countered with a perfect tee shot down the middle of the fairway, landing some 200 yards from the hole.

Hughes birdied the par-5, putting him 2 up, and then nailed his tee shot on the 145-yard No. 16, landing 3 feet from the pin. Hughes sprinted up the fairway “more because I was feeling the nerves in my hands and legs,” he said. “I wanted to get that out of my system. And to check how close? That, too.

“Today my thinking was trying to stay within myself. Out here, if you stay within yourself, stay right around even par, that is a good mark. (Nos.) 13 and 14 can be difficult, so my thinking was, OK, as long as I got to 15 it would be smooth sailing.”

Both agreed that they were well-matched, having the same playing pace, and would enjoy playing together again, as well as in this event.

“Today was pretty relaxing and one of the best rounds of golf I’ve played,” said Ah Mow, playing OCC for just the fourth time. “I’m looking forward to playing next year here and years to come.

“Hunter is an awesome guy. I want to play with him later.”

“Caleb was really impressive for an 18-year-old kid. I wasn’t there at that age,” Hughes said. “There was a home-course advantage, I’m playing Oahu Country Club almost every day, and that is a privilege.

“Those of us who play here talk about the mana of the valley, how you have to give this course a lot of respect. It’s hallowed grounds.”

Play continues today with the men’s second-round matches and women’s quarterfinals. The women’s 18-hole championship is Friday and the men’s 36-hole championship Saturday.