Sean Austin fingered his coral beads, tucked his gold chain into his white T-shirt, and casually put his hand into his front pocket. In the early evening twilight, the cooling sun beat lightly on Austin, a 4-6, 6-1, 6-2, winner yesterday over David Tremaine in the final of the Greater Washington Area Boys High School tennis championships at Rock Creek Stadium.

His older sister's boyfriend, Rodney Harmon, strolled across the soft green clay and offered his congratulations.

Austin has known Harmon, ranked 61st in the world, almost two years. "That's how long he's been going out with my sister Janine."

Austin, 17, a senior-to-be at St. John's High School, speaks softly and carries a strong forehand, also a trademark of Harmon's.

Harmon is, Austin admits, a role model. "He sure is. There are not too many black people in tennis, besides (Yannick) Noah, and we've talked a little bit about it, but not too much.

"Rodney is really teaching me to be tougher mentally. A strong mental game goes farther."

Austin, unlike his opponent, displayed his cool during the 1 1/2-hour match. In the first set, Austin used a fine forehand passing shot to go up, 3-1. Tremaine angrily slapped the ball into the net.

Tremaine, who attends Rockville High School, broke back and held to tie the match at 3, and then broke to go up at 5-4, with aggressive serves and volleys. "He could have beaten me," said Austin. "But then I started lobbing better."

A combination of top spin lobs and some strong returns off Tremaine's deep serve helped Austin control the second set. "I think the turning point was when I broke him the first time in the second set and then he served those four double faults (Tremaine was down by 4-1 at the time).

"I've never seen that, ever," said an amused Austin.

In the third set, Austin broke immediately in the first game and jumped out to a 4-1 lead by consistently lobbing over an exasperated Tremaine.

Tremaine made one last ditch effort, breaking to get back to 4-2. But, Austin controlled the tempo the rest of the match, winning on a backhand volley that Tremaine netted.