Vegas, a Venezuelan who attends the University of Texas and lives in Austin, had the toughest time, outlasting 15-year-old Cheng Tsung Pan of Taiwan, 2 and 1. Colt Knost (Southern Methodist) defeated Canadian Nick Taylor 4 and 3, and Casey Clendenon (Lamar University) knocked off Californian Eddie Olson 4 and 3.
Michael Thompson of the University of Alabama became the last semifinalist, after he defeated Derek Fathauer 5 and 4. Thompson will face Clendenon on Saturday in the 18-hole semifinal, while Vegas and Knost will meet in the other match.
Pan had already made history before losing to Vegas. He was the youngest quarterfinalist since Bobby Jones, who was 14 when he reached the same round in 1916. His chipping was a major factor in his first three match-play wins, and it kept him in the match against Vegas -- but after getting within one hole after the eighth, he could get no closer.
Clendenon was also an unlikely quarterfinalist because he almost didn't get to match play. The 315 qualifiers for the event played two rounds of stroke play to cut the field from 315 to 64, and Clendenon parred his last two holes to get into a playoff, and then birdied the second hole to advance.
The key to his win over Olson was solid play from bunkers on the fourth and fifth holes.
'After that, I just stayed patient,' said Clendenon, who was the Southland Conference Player of the Year in 2006. 'To win the U.S. Amateur obviously you've got to be putting very well, and I think I'm putting very well right now.'
Thompson also credited his success so far to his putting.
'My putting today was excellent,' he said. 'I'm getting more confident on the greens.'
Thompson also hit an excellent shot on the uphill 286-yard, seventh hole, driving to within a foot of the hole. Fathauer conceded the eagle, which put Thompson 2-up, and the match never got any closer.
Colt Knost continued his fine play Friday, and is the only semifinalist already on the Walker Cup team, because of his U.S. Public Links championship. This is the fourth time Knost has qualified for the Amateur, but this is the furthest the 2007 C-USA Player of the Year has advanced.
'Today I hit it really good,' he said. 'The hard part is getting it in the fairway, though.'
Knost is playing with a lot of confidence.
'I give away very few holes with bogeys,' he said. 'I make people make birdies to beat me, and I think that's the biggest thing to do out here.'