Co-Medalist Chen, Diaz-Yi, Santos, Yang Advance to Semis June 20, 2013 | Norman, Okla. By David Shefter, USGA

Doris Chen won her second consecutive 19-hole match to reach the semifinals of the 2013 U.S. Women's Amateur Public Links Championship. (USGA/Joel Kowsky)

Two Southern Californians, the stroke-play qualifying co-medalist and an Oklahoma collegian advanced to the semifinals of the 2013 U.S. Women’s Amateur Public Links Championship after winning quarterfinal matches on Friday morning at the Jimmie Austin OU Golf Club.

Lauren Diaz-Yi, of Thousand Oaks, Calif., and Raychelle Santos, of La Quinta, Calif., will meet in one semifinal on Friday afternoon, while the second match will feature co-medalist Doris Chen, a member of the national-champion University of Southern California team, against Julie Yang, a sophomore at Oklahoma State University.

Santos, a 19-year-old sophomore at Gonzaga University, eliminated Cindy Ha, 16, of Demarest, N.J., 2 and 1, while Diaz-Yi, an 18-year-old incoming freshman at the University of Virginia, posted a 4-and-3 win over Krystal Quihuis, 16, of Tucson, Ariz.

Chen, playing in front of the largest gallery of the morning, outlasted University of Oklahoma senior Anne-Catherine Tanguay, of Canada, in a 19-hole thriller, preventing an all-Bedlam matchup against Yang. The Oklahoma-Oklahoma State Big 12 rivalry is called the Bedlam Series.

The Korean-born Yang, who earned All-American honors as a freshman at Oklahoma State this spring, defeated 2008 U.S. Girls’ Junior runner-up Karen Chung, 2 and 1, in the last of the quarterfinal matches. With OSU women’s coach Alan Bratton on the bag, the 17-year-old Yang won three consecutive holes from No. 12 after trailing the first 11 holes.

The most dramatic match of the morning was between the 20-year-old Chen and Tanguay, who never trailed the entire week until the 19th hole against Chen. Tanguay went 1-up on No. 11 by converting a 7-foot birdie putt. The match remained that way until the par-5 18th hole, with Chen staying alive on No. 17 by holing a 10-foot par putt to halve the hole.

At the par-5 18th hole, Chen, of Bradenton, Fla., faced a challenging 100-yard shot to a hole location tucked tightly in the front portion of the green. Chen needed a perfect shot and executed it, landing her pitching-wedge approach 6 feet to the right of the flagstick. When the 21-year-old Tanguay failed to convert her 30-footer for birdie, Chen forced extra holes by holing her putt.

For Chen, it was her third consecutive match that went the distance, and second in a row going 19 holes.

"I didn’t know if I was going to win or not, but I just wanted to try the best I could," said Chen. "To be honest, I was a little nervous on the 18th and 19th [holes]."

On the 19th hole – the par-4 first hole at the Jimmie Austin OU Golf Club – Chen failed to reach the green in regulation. Her third shot stopped 10 feet from the hole. Tanguay caught a flier for her approach from 156 yards that was just off the putting surface and she rolled her putt to 8 feet. Chen made another clutch putt, while Tanguay’s lipped out.

"She played well, so she deserved it," said a gracious Tanguay. "I think I did all I could do."

Not only was Chen battling a tough opponent in Tanguay, but also a pro-Sooner gallery that was heavily rooting for the OU standout. Chen said she just tried to focus on her game and not any outside influences.

"The crowds are great," said Chen. "They are very polite."

Yang, coming off playing 39 holes on Thursday, needed only 17 against Chung, an incoming USC freshman from Livingston, N.J. At times, the golf wasn’t stellar – she won No. 13 with a bogey-6 – but she did enough to advance.

"I think I’ve played pretty steady this whole week," said Yang. "Some days, my ball striking wasn’t as good as others, but overall, I’m pleased."

Of the four semifinalists, Santos has the least experience on the national stage. Diaz-Yi reached the quarterfinals of last year’s U.S. Girls’ Junior and lost a second-round match at the U.S. Women’s Amateur to 2012 USA Curtis Cup Team member Lisa McCloskey. Yang has won events around the world and Chen, the 2010 U.S. Girls’ Junior champion, will play in her second U.S. Women’s Open next week in Southampton, N.Y.

"It’s like a Gonzaga story again," said Santos of her school, which used to be a major underdog in college basketball. "I wasn’t really nervous because I made it this far. I was just going to go out and have fun."

Santos never trailed in her match against Ha, who plans to enroll at Vanderbilt University in 2014. Santos won consecutive holes with pars at 13 and 14 for a 2-up lead. Ha would get one back with a par at 16, but Santos ended any comeback hopes by taking No. 17 with a par.

"I came into this tournament just wanting to make match play because I played [the 2011 WAPL] in Oregon [at Bandon Dunes] and I didn’t make match play," said Santos. "Putting definitely [has been a key]. My speed and everything has been good. Everything inside six feet has been going in."

Diaz-Yi said she has leaned heavily on her 2012 USGA experiences, which included making match play at the WAPL, Girls’ Junior and Women’s Amateur. She said her swing has gotten more on plane and her putting has improved since last summer.

She is also pacing herself in the Oklahoma heat.

"I drink my water, my Gatorade and just try not to exhaust myself mentally," said Diaz-Yi.

Diaz-Yi took a 3-up lead into the turn, including an eagle-3 at the par-5 eighth hole. She also won No. 10 to go 4 up and cruised from there to set up a match against good friend Santos.

"I love Raychelle, she’s a sweetheart," said Diaz-Yi. "I think we’re going to have a lot of fun since we know each other really well. It won’t be as tense as I might be with another player."

David Shefter is a senior staff writer with the USGA. Email him at dshefter@usga.org.