SAN FRANCISCO (AP) -- Top-ranked amateur Jackson Koivun didn't make a birdie until his final hole for the second straight round in the U.S. Amateur. The difference Thursday was he was eliminated at The Olympic Club, along with three others from the top 10 in the world amateur ranking.
Oklahoma State junior Preston Stout, the medalist in stroke-play qualifying and the No. 4-ranked amateur, became the only player from the top 10 to advance, taking the lead for the first time on the 13th hole before winning, 2 and 1, over David Liechty.
Koivun, who tied for fifth in the Wyndham Championship on the PGA Tour two weeks ago, squeaked by in his opening match. He wasn't so fortunate in the second round, as Illinois junior Max Herendeen took the lead on the seventh hole and led the rest of the day, winning 3 and 2.
Virginia senior Ben James, the No. 2 amateur in the world, made bogey on the 18th hole to lose to Mason Howell, the 18-year-old from Georgia who qualified for the U.S. Open this year with rounds of 63-63 from the Atlanta sectional.
Two other players from the top 10 failed to advance.
Niall Shiels Donegan, who won the last two holes with birdies for a 1-up victory over Luke Poulter on Wednesday, took down Christiaan Maas of South Africa (No. 9 in the amateur ranking), 1 up. Donegan, who plays under the Scottish flag and lives in the Bay Area, birdied the par-5 17th hole for a 1-up lead and the 18th hole was halved with pars.
Pepperdine senior Mahanth Chirravuri took a 2-up lead on the fifth hole and seventh-ranked Jase Summy could not get any closer as Chirravuri advanced, 3 and 2.
Also advancing was John Daly II, the son of two-time major champion John Daly, who beat Nate Smith, 2 and 1.
The round of 16 was Thursday afternoon, with the quarterfinals scheduled for Friday.
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