The check was presented and the check was given back.

Micki Shillig, a senior-to-be at San Diego State, was delighted with her first victory in a professional tournament yesterday. But, because she is an amateur, the $1,400 had to be returned.

Shillig won the Toyota Women's Tennis Classic by beating Phyllis Blackwell, 6-1, 6-7 (8-6), 6-0. Her powerful serve and aggressive ground strokes could not have been more precise than they were in the final set.

"I didn't think I should have lost the second set," said Shillig, 21. "I wasn't hitting out like I was in the first set. I knew I had to be more aggressive. But sometimes you just do dumb things out there."

Shillig was third-seeded in the tournament, held at the Landon School in Bethesda. Blackwell was seeded second. Friday, Shillig had defeated top seed Kate Brasher. That's two impressive victories in a row, but, said Shillig, "I don't think I'm ready to try the pros yet." She first would like to improve on her 1982 second-place NCAA singles finish. "This is enough right now."

Shillig, from Cedar Rapids, Iowa, appeared to be in command from the start, taking a 3-0 lead in the first set before Blackwell won a game. After being down a game point at 3-1, Shillig won 11 of the next 13 points to take the set.

The way the second set began, it appeared that the 50 or so spectators would be going home early. Shillig served two aces and quickly moved to a 4-1 lead.

But Blackwell, from Mobile, Ala., held serve, then a cross-court passing shot brought her to 3-4. Blackwell again held serve and broke serve to move to 5-4, only to stroke away a set point in the next game and find herself in a tie breaker.

She fell behind, 4-2, surged to 6-4 and was tied at 6-6. Taking a deep breath, she forced Shillig to miss, then hit a forehand winner. Match even. Third set.

Twenty-two minutes later, Shillig put away an easy volley for victory. Blackwell, 25, was limited to nine points that set, the final point coming with Shillig at the net.

Shillig had reached two quarterfinal rounds and one semifinal round in her previous four tournaments this summer. So she had given back money before.

"It was only a blank envelope, anyway," she admitted.