Of the players remaining in the main draw of the USTA National Boys' 18 and 16 Clay Court Championships, there is just one local.

That local, Jared Pinsky, knows what it's like to stick around in the late rounds of a tournament.

A junior at Churchill, Pinsky won the Maryland state tennis championships in May for the second year in a row. Yesterday, the fifth seed knocked off top-seeded William Guzick, 6-4, 7-5, to claim his spot in the boys' 16-and-under singles semifinals. He will play No. 9 seed Tyler Hochwalt of Scottsdale, Ariz., at Woodmont Country Club in Rockville at 10:30 a.m. today.

"It was a very tough match, but I played well," said Pinsky, who won in temperatures hovering in the 90s. "In the second set I got a little bit tired, but luckily, I got my energy and kept fighting out. . . . He looked pretty tired, too, at the end."

Guzick, who was born in Potomac but moved to South Carolina when he was 5 years old, led the first set 4-3 before Pinsky rattled off three straight games.

Pinsky was helped along in the second set by the crowd, which was overwhelmingly in his favor.

Down 4-2 in the second set, Guzick battled back for a 5-4 lead. But to the delight of the crowd, Pinsky pulled through. Down 40-love with the set tied at 5, Pinsky, in his second shirt of the match, rushed the net after returning a serve and pounded an overhead. Later, Guzick's double fault made it deuce and an eventual Guzick volley landed long at Pinsky's feet, leading him to jump and pump his fist as he took a 6-5 lead. A deuce in the final game was broken by Pinsky's ace that wowed the crowd. Then Guzick returned a volley into the net to give Pinsky the victory.

"Jared played very well," Guzick said. "His down-the-line forehand was really good. On his serve he really got to my backhand well. I just didn't have the energy I needed. . . . I was just too nervous."

The win puts Pinsky one step closer to earning a wild card into the singles qualifying event of the Legg Mason Tennis Classic, held at the William H.G. Fitzgerald Tennis Center in Washington from July 30 to Aug. 7.

"It's big," Pinsky said of the Legg Mason. "It would be nice to get into the qualifier of that if I can win this. It would be a lot of fun to play against those guys."

Alexander Clayton, at No. 3, is the highest seed left in the boys' 18 singles. He has yet to have his serve broken in the tournament. Top-seeded Mykyta Kryvonos lost in the third round to unseeded Christian Welte and second-seeded Timothy Smyczek was bounced by ninth-seeded Sasha Ermakov.