Defending champion An among four to advance to U.S. Amateur semifinals

Peter Uihlein put his hands out with an almost apologetic look on his face after dropping a 5-foot putt to win his quarterfinal match at the U.S. Amateur on Friday. Beating his college teammate, and one-time roommate, wasn't very enjoyable for the top-ranked American amateur. "It's bittersweet. I just took out one of my best friends. It's hard because seeing him after, he wasn't happy," Uihlein said of his 1-up win over Oklahoma State teammate Morgan Hoffmann. "It's hard for me to be excited when I just played him." Uihlein's victory over Hoffmann was one of four highly competitive matches in the quarterfinals of the 110th Amateur at Chambers Bay. A day after only a few of the 24 matches even reached the 17th or 18th holes, all the quarterfinals made it to at least No. 18, with Patrick Cantlay needing 20 holes to win his match. Uihlein and Cantlay will meet in one semifinal on Saturday morning. The other will be a Cal-Stanford matchup, with defending champion Byeong-Hun An facing Stanford's David Chung. In another matchup of college teammates, An beat Max Homa 1 up, while Chung dropped an 8-foot putt on the 18th to take out reigning NCAA champ Scott Langley of Illinois. It's a power trio with Uihlein, Chung and An, joined by a relative unknown in Cantlay, who finished tied for second during stroke play and has quietly advanced to the semifinals. Cantlay needed 20 holes in the quarters, taking advantage of Jed Dirksen's three-putt on the 18th green when Dirksen held a 1-up lead. An is the first defending champion to reach the semifinals since Tiger Woods in 1996. He's also trying to become the first back-to-back champion since Woods won three straight titles between 1994 and 1996. "I definitely passed my goal," An said. "I'm really happy I'm here right now. I guess I'll be more happy if I get to the finals and win." Uihlein and Hoffmann were the top two players on an Oklahoma State squad that lost in the NCAA team finals to Augusta State. They might be the top two players in the field, but fell into the same bracket after the first two days of stroke play. Their match was as competitive as expected with neither holding more than a 1-up lead. Uihlein went in front for good with a birdie on the par-4 16th as a train roared by on the nearby tracks. They halved the final two holes, with Hoffmann missing his birdie attempt that could have sent the match to extra holes. "I wasn't as on as I have been. That's the way it goes," Hoffmann said. "We're both Cowboys and hopefully he goes on and wins it for the team." After two days of routs in his first three matches, An was finally forced to see Nos. 17 and 18. He hadn't played beyond No. 16 in reaching the quarterfinals, but was forced to the final two holes by Homa's backside rally. Homa won the 17th to cut An's lead to 1 up, but his third shot on the par-5 18th came up short and Homa wasn't able to make the birdie that would have extended the match. Cal coach Steve Desimone stood to the side of the 18th green, meeting both of his players as the match ended. "We played great golf today," An said. "That's why I was very tired. We didn't make that many mistakes." Chung might be the hottest amateur in the United States entering the Amateur, having won the Western Amateur and Porter Cup leading up to the event. The Stanford junior finally pulled ahead of Langley with wins at the 14th and 15th holes, and had a chance to finish the match, but missed his birdie attempt on 17. Langley forced one more hole by making a 25-foot birdie putt at No. 17 and reached the 18th in two, stinging a 3-wood from 260 yards to about 50 feet. Langley's eagle putt raced past and Chung's birdie ended Langley's hopes. "I think you can't not think about the prize," Chung said, noting that finalists receive an invitation to the Masters. "... But I think you have to stay grounded. It's nice to think about how great Sunday could be if you get there, but just stay grounded and stay in the moment -- try to at least." Dirksen was a favorite of many fans, going without a caddie and carrying his own bag during the tournament. He was 1 up headed to the 18th, but left his third shot at the bottom of a ridge and three-putted to give Cantlay another chance. They parred the first extra hole, before Cantlay won with a par at the second. "There are a lot of things going through your head just standing there and waiting for whatever happens to happen," Cantlay said.