CdM junior John Davenport shot 78, but missed the cut by one stroke. Newport Harbor junior Carter Norris shot 79 and Norris' teammate, senior Zach Eddy, shot 82.
Only three players broke par on the 6,800-yard, par-72 layout.
Trauthen took the event in stride.
"I just played how I normally play; not do anything stupid and take what the course gives you," he said. "I didn't feel that much pressure. It was a bit more pressure [than at Pacific Coast League finals]. The competition is better and you're playing with people you've never met."
Knapp was an exception in that regard. He and UCLA-teammate-to-be, Servite senior Preston Valder, played in the same group. Knapp, the Orange Coast League champion, has verbally committed to UCLA.
Cerritos senior Kevin Lee earned medalist honors with a four-under 68 while Valder and Mater Dei's Brian Campbell each shot 70.
Players teed off beginning at 7 a.m. in shotgun format. Calm conditions prevailed for much of the tournament, but players faced moderate wind gusts on the finishing holes.
Trauthen said putting was difficult. Players had to manage contoured greens on many holes.
Knapp, reached by phone after the round, eagled the par-four first hole. He said the tees were moved up, making the hole 290 to 300 yards. Knapp hit three-wood to 15 feet of the hole and made the subsequent putt. He added two birdies, but struggled getting into a rhythm.
"I struggled all day on the greens," Knapp said. "I had short putts I normally don't miss. Low numbers were out there."
"The greens were more receptive than I thought they were going to be," Trauthen said. "I had some shots that spun 20, 30 feet back."
Trauthen's one birdie came at the par-five third hole. His third shot from 90 yards stopped two feet from the hole and he made the birdie putt.