The USTA National Amateur Indoor Tennis Championships are rapidly turning into the John Zahurak show. On Thursday, the 17-year-old Calvert Hall (Baltimore) senior toppled top-seeded Stevenson Clarke. Yesterday, at the Crystal City Racquet and Health Club, it was 13th-seeded Jeremy Semple's turn to lose to Zahurak's big serve, 6-0, 7-5.

When Zahurak jumped ahead, 4-2, in the second set, the match appeared to be over. However, Semple, a Stanford sophomore out of Sidwell Friends, rallied for a 5-4 lead. Then at 5-5, Zahurak led, 40-0, on Semple's serve before hanging on to win a marvelous eight-deuce game. Zahurak then served out the match.

"In the second set, he cut down his errors and starting putting more pressure on me with his first serve," Zahurak said. "But I knew if I got my first serve in, I'd be all right."

The semifinal opponent for Zahurak, three-time defending Maryland state scholastic champion, will be eighth-seeded Roberto Saad of Argentina and Wichita State, who defeated No. 3 Josh Sarner, 6-4, 6-4. Fifth-seeded Phil Tuckniss beat No. 4 Paul Annacone, 6-3, 7-5, and faces No. 14 Danny Goldie of McLean, who downed seventh-ranked Ahmed El Mehelmy of Egypt, 6-4, 4-6, 6-2.

Goldie, formerly of Bullis, and now Stanford's No. 2 player as a freshman, is the only Washington-area player remaining. Goldie attributed his victory to "my serve and volley. He never came to the net. I came to the net as much as I could and hit it as hard as I could."

The top four seeds advanced to the women's semifinals. No. 3 Connie Yowell of Yale defeated Bethesda's Jan Shelburne, 6-1, 6-2, while defending champion Kathleen Cummings routed Arlington's Amy Kneale, 6-0, 6-1. Second-seeded Joy Cummings of Princeton edged crowd favorite Eleni Rossides, 15, of Sidwell Friends, 2-6, 6-2, 6-4. The wild final set included five service breaks and a double fault by Cummings on match point.

Third-seeded Jennifer Goodling of York, Pa., and Rollins College got past No. 5 Laurie Macgill, 3-6, 6-2.