Renee Richards, playing her first competitive tennis since undergoing surgery on an achilles tendon last September, upset sixth-seeded Virginia Ruzici, 5-7, 6-1, 7-5 in the first round of the Avon championships at George Washington University's Smith Center last night.

"I've beaten Rosie (Casals) and Kerry Reid," said Richards. "But this is one of the best wins I've had."

Ruzici was playing her first match since sustaining a muscle pull in her leg a month ago. Ruzici seemed in command, breaking Richards in the third game of the third set for a 2-1 lead, after Richards lost 10 straight points.

But Richards, 44, who last year was known to tire early, came back in a flurry at the end of the set, breaking Ruzici in the 10th game to tie at 5-5.

Richards then held her serve and broke Ruzici for the 7-5 win.

Earlier, Richards had fought off a match point while serving in the ninth game of the final set, keeping her alive in the $125,000 torunament, first stop on the women's indoor tour.

"It's really disappointing to start back this way," said Ruzici, the world's 12th-ranked woman player. Richards is rated 27th.

"I just couldn't concentrate well," said Ruzici, "especially when I needed it -- when I was up 5-4 and serving.

"I let her attack me. There I was. I went down all of a sudden.

The final game went to deuce, and Richards then won the next two points, passing Ruzici with a backhand and forcing her to hit a forehand long.

This is the beginning of Richard's second year on the tour, following her much publiczed sex-change operation.

"Renee was serving really well," said Ruzici. "I've always had trouble against lefthanders."

This was the first meeting between the two players, although Richards said she has often practiced with Ruzici.

"It was difficult to come up with a game plan against her, because Virginia of today is different from Virginia of last year," said Richards. "She has truly become a world class top ten player.

"I couldn't have it in my plan to just hang on and wait for her to make errors, because she doesn't do that any more. I had to attack, try to make volleys."

The match lasted an hour and 45 minutes, drawing spirited responses from the crowd of less than 2,000.

Fourth-seeded Dianne Fromholtz beat Jo Anne Russell 6-2 in their first set and then won the match by default, leading 2-1 in the second. Russell, a quarterfinalist in Washington last year, injured her right ankle and could not continue.

Yesterday's earlier matches went according to form.

Ruta Gerulaitis, the younger sister of Vitas, defeated Dana Gilbert, 6-4, 6-4, to advance to the second round of the $125,000 tournament, which concludes Sunday.

Ilana Kloss faced five set points before managing a 7-6 win in the first set over Laura DuPont, and went on to defeat the Matthews, N.C., native, 7-6, 2-6, 6-4.

DuPont was bedeviling Kloss with fine drop shots, but Kloss became more aggressive and took control of the match, scoring on passing shots and forcing DuPont into errors.

The DuPont-Kloss match was the longest and most exciting of the early matches. Maureen (Peanut) Louie disposed of Viviana Gonzales, a finalist in last summer's U.S. Clay Court championships, 6-4, 7-6. Louie won the tie breaker in the second set, 7-1.

Ann Kiyomura, more noted for her doubles play, beat Jeanne DuVall, 6-4, 6-2.

Janet Newberry eliminated Caroline Stoll, 6-2, 6-2.

Martina Navratilova, the defending champion and top seed, opens play tonight against Lea Antonopolis, and second-seeded Tracy Austin will see action Wednesday against Barbara Halquist.

Seventh-seeded Pam Shriver will meet Francoise Durr tonight.

In yesterday's preliminary qualifying match, Nancy Ornstein of Washington beat Zenda Liess, 4-6, 6-3, 7-5. Ornstein will play Mima Jausovec this morning.