Tony DeLuca, 21, from Vienna, Va., was acting like nothing had happened, pottering about on the putting green and trading jokes with his caddie.

But the man, who was considered so unlikely to figure in the shake-up stages of the U.S. Amateur Golf Championships that the USGA hadn't bothered to prepare a profile sheet on him, today upset Corey Pavin, 3 and 1. Pavin is a member of this year's U.S. Walker Cup team, the 1977 Junior World Golf champion, winner of the North and South Amateur and the Southwestern Amateur, and the second-leading qualifier out of 282 competitors in this championship.

DeLuca, a student at the University of Florida, wasn't at all surprised at his feat, which followed hard on the heels of the elimination of defending champion Hal Sutton.

"Nah, I knew I could do it, the way I was playing," said the soft-spoken DeLuca, who was Virginia State high school champion in 1978 and the joint leading qualifier from the Virginia area for the championship proper.

"Today I hit 13 of 17 greens," he said.

"I was disappointed with my game in the qualifying round this week," said DeLuca, who scored a 154, with two 77s on the lake and ocean courses that are in use for this championship. "I've been hitting the ball very solid and it was only a matter of time before it came right. In fact if this keeps up I think I can win it," he said.