LOS ANGELES—Imagine standing in the shadow of the Swinging Bridge, facing a hometown player with the crowd on their side, staring down a 4-foot left-to-right slider with your place in a national championship hanging in the balance. Now imagine that the greatest putter of all time, Ben Crenshaw, is one the edge of Bel-Air Country Club’s 18th green, watching intently. Bentley Cotton, a junior at Texas, was confronted with that terrifying scenario on Wednesday, during the first round of match play at the U.S. Women’s Amateur. Cotton made a confident stroke but hit the par putt too hard, and just like that she was eliminated from the Am.

Watching the putt slide by the hole, Crenshaw winced as if someone had smashed his shin with a 7-iron. “Oooooh, you hate to see that,” he cried out. He is friends with Cotton’s parents and has been a mentor to Bentley.

Cotton’s opponent, Caroline Corales of UCLA, had been 2 down at the turn but battled back with birdies at 14 and 15. “Survive and advance,” she said afterward, the mantra for every player who is still alive at Bel-Air. “Every match is a grind and a test. You just have to keep battling.”

The first round of match play at the Women’s Amateur is one of the best days in golf, a dawn-to-dusk stress-fest. (Wednesday began at 7 a.m. with a 10-for-9 playoff to fill out the bracket.) Of the 31 matches in the first round—Rin Yoshida advanced by forfeit when her opponent, Lauren Miller, had a medical emergency—six went to sudden death and five more reached the 18th green. Hailey Borja, a four-time All-Big Ten selection at Michigan, had been 3 up at the turn but her scrappy opponent Megan Meng stormed back to tie the match through 17 holes. Sitting next to the 18th green as both players sized up challenging chips, Meng’s friend Noe Novella  took long, deep breaths and lamented, “I’ve barely been able to breathe this whole back nine!” Borja’s deft up-and-down closed out the match. Novella was elated, but Borja looked merely relieved.

Other keynote winners were pushed to the limit: Oregon senior Briana Chacon survived the curse of the No. 1 seed, prevailing on the 19th hole over Olivia Duan (six of the last nine No. 1s had fallen in the first round of match play); Stanford’s Rachel Heck, continuing her comeback from having a rib surgically removed, outlasted Japan’s Sera Hasegawa in 21 holes; and Casey Weidenfeld (below), an all-freshman selection at Auburn last season, had the comeback of the day, roaring back from 4 down with five holes to play against Thanana Kotchasanmanee of Thailand. When Weidenfeld won the 22nd hole to end the match, it was the first time all day she had tasted the lead.

Another overtime winner was Taylor Riley (top, in yellow), a sophomore at LSU, who outlasted Colorado’s Morgan Miller on the 20th hole. Riley’s dad, Chris, is a former PGA Tour winner who now coaches the men’s team at the University of San Diego. He caddied for Taylor during the practice rounds, but once the tournament began in earnest, mom Michelle has been on the bag. “My dad gets a little too nervous when I’m playing in tournaments so he lets her handle me,” says Taylor with a laugh. Michelle played at LSU and exudes a quiet competence as a caddie, but she admitted that two bad club selections led to mistakes that helped Miller rally on the back nine. “I took full responsibility,” says Mom, “but on [the par-3] 16 I tried twice to pull her off so it was really her fault. But I still  took full responsibility.”

Taylor has a laggy, athletic swing that evokes the young Sergio Garcia. Her dad was a preeminent putter, but she says, “That’s something I’ve had to work hard on. I’m hoping those genes kick in a little harder.”

Commitment is not a problem for this ambitious young woman: Taylor had an early-morning practice round last Saturday so she skipped a Taylor Swift concert the night before as Chris took her younger sister, Rose. Asked how she would celebrate her first-round win, Riley said, “Eat some snacks and get some sleep. Gotta keep my energy up.”

Indeed, if the first round of the Women’s Amateur is defined by the wall-to-wall action of so many matches finishing in rapid succession, Thursday is a war of attrition, with the second round being conducted in the morning and then the Sweet 16 in the afternoon. “It’s great to win your first match,” said Canales, “but the hard part is still to come.”

The USGA is a partner to the Fire Pit Collective but has no editorial oversight.