Woods Advances to Quarterfinals : Golf: Defending U.S. Amateur champion wins twice. Tidland and Gibson lose in second round.

Defending champion Tiger Woods of Cypress won two matches Friday to reach the quarterfinals of the U.S. Amateur. The other two Orange County golfers who reached match play, Chris Tidland of Placentia and Scott Gibson of Huntington Beach, lost in the second round.

Woods, who had only one bogey in 33 holes, defeated Chad Campbell of Andrews, Tex., 4 and 2, and then ousted Sean Knapp of Oakmont, Pa., 2 and 1. Knapp beat Woods’ Stanford teammate, Notah Begay, to reach the field of 16.

Woods said he has become comfortable on the slick greens and wind-swept fairways of Newport Country Club. A five-over-par 75 in the second round of stroke play served as a wake-up call.

“I knew I couldn’t afford to make mental mistakes,” he said. “I feel very confident with my game now.”

This morning, Woods will face Scott Kammann of White Pine, Tenn. Kammann, whose wife of one week caddied for him, beat Marc Spencer of Bradford, Mass., 2 and 1.

Tidland, a runner-up in the NCAA Championships in June, was eliminated by George Marucci of Berwyn, Pa., on the 20th hole. Gibson lost, 2 down, to Chris Riley of San Diego. Marucci reached the quarterfinals, Riley did not.

Steve Scott, 18, of Coral Springs, Fla., defeated Griff Moody, 37, of Hoover, Ala., 5 and 4 to reach the round of eight. Scott, who would replace Woods as the youngest U.S. Amateur champion if he wins here, was five under through 14 holes, including birdies on 10, 11, 12 and 13.

Mark Plummer, 43, of Manchester, Maine, also won twice Friday. Plummer, a liquor salesman with a large mustache and unorthodox swing that nearly causes him to fall down on his follow-through, beat Matthew Goggin of Tasmania, 2 and 1.

The four quarterfinal winners will play this afternoon. The 36-hole final is Sunday.