Trauthen shot 81 with a birdie-birdie finish on holes 12 and 13. Twenty-eight of 109 players advanced to next week's CIF/Southern California Golf Assn. Southern Regional, the final step before the CIF State Tournament.
Knapp reached the CIF/SCGA last year after finishing third at Lompoc's La Purisima Golf Course.
He entered Monday's event with a driver he'd never played before. Knapp, the Orange Coast League champion, said he cracked his other driver hitting balls on Sunday.
The club change caused him to alter strategy.
"I hit more three woods," Knapp said. "Not knowing your driver is crucial."
Knapp, recalling his round, started with a birdie on the par-four ninth. Golfers teed off in a shotgun format. He followed with a par on No. 10, but struggles started on the par-five 11th.
Knapp hit into the trees and three-putted en route to a double-bogey.
"I was too aggressive," Knapp said of the 11th hole. "I was behind the rest of the day."
Knapp parred three of his last six holes. He three-putted for bogey on the par-three seventh and missed a five-foot birdie putt on No. 8, an uphill, dogleg-right par four.
Trauthen, making his first appearance in the event, started on No. 14 and began four-over through his first three holes. He two-putted for par from 40 feet off the fringe on 17 and tallied his first of three birdies on the par-five 18th. He hit his third shot to within 3 feet of the hole and made the putt.
Trauthen parred two of his next three holes, but said he never felt comfortable with either the three wood or a hybrid club he uses.
"I tried to be more conservative, but I'm not the most conservative player," Trauthen said. "I couldn't hit either [the three-wood or hybrid] off the tee.
"The start was really rough and I couldn't recover from that. I couldn't swing today until the last couple of holes. I couldn't find anything."
Glen Lee, a freshman from Valencia of Valencia, and Villa Park junior Kethan Reddy tied for low round at one-under 70.