Tracy Austin yesterday turned what was expected to be a tough duel with Hana Mandlikova into a quick and efficient execution; Andrea Jaeger made a splendid comeback from 1-5 down in the third set and saved a match point in beating Virginia Ruzici, and Chris Evert Lloyd defaulted because of flu. It was, in short, just your average, soap opera day of women's tennis in the $250,000 Colgate Series Championships.

Austin, scrambling so well that she got to shots even she didn't think she could reach, trounced Mandlikova, 6-3, 6-0, last night to assure herself a place in the semi-finals.

Then Martina Navratilova got a free ride into the semis because of Evert's default. Evert had a 102-degree fever, severe sore throat and other flu symptoms, and decided after being examined by tournament physician Dr. Stephen Haas that she wasn't up to playing.

Austin and Navratilova now have 2-0 records in this elite, eight-woman playoff for the top finishers in the worldwide 1980 Colgate Series of 39 tournaments, and move directly into Saturday evening's semifinals. They have today off.

Jaeger and Wendy Turnbull, the youngest and oldest players in the tournament, kept alive their chances for semifinal berths with victories yesterday afternoon.

Jaeger, 15, a born fighter with the poise of a champion twice her age, showed her spunk by fighting back from 1-5 down in the final set, saving a match point at 4-5, and ultimately beating Ruzici in a tie breaker, 3-6, 6-2, 7-6.

Turnbull, 28, a journeywoman who played some of the best tennis of her career last year, beat Pam Shriver of Lutherville, Md., 7-5, 7-5. The last time they had met, in the final of a tournament in Sydney the first week of December, Turnbull won after saving seven match points, and again she proved a little tougher psychologically at the critical stages.

Ruzici and Shriver now have 0-2 records, and are out of the running for the $75,000 first prize that will be decided Monday evening.

Mandlikova, Jaeger, Turnbull and Evert have 1-1 records, and are scheduled to play tonight. Mandlikova will face Turnbull at 7 p.m., followed by Evert versus Jaeger, provided Evert recovers sufficiently to play.

The two players who emerge with 2-1 records will join Austin and Navratilova in the semifinals, while tonight's losers will be eliminated.

Rosemary Casals and Turnbull defeated Shriver and Betty Stove, 6-4, 6-4, last night to advance to tonight's doubles final against Paula Smith and Candy Reynolds.

Jaeger's gritty comeback breathed some life into yesterday's matinee session, played before 2,600 spectators. But the inviting prospects for the evening program fell flat when Austin routed Mandlikova in less than an hour, and Evert had to default.

Navratilova played a one-set exhibition, beating Mima Jausovec, 6-3, then took the umpire's microphone and told the audience of 8,500: "I'm really sorry Chris was sick and couldn't play tonight. I hope she can come back and play tomorrow. I want to thank you all for being so understanding."

Later, she said she was as disappointed as the paying customers about the unfortunate turn of events.

"It was one of the strangest things, because I was really psyched up and ready to go today," said Navratilova, who beat Evert in the 1978 and 1979 Wimbledon finals and lost to her in the semifinals there last year. "I was really nervous the whole day. I was hitting well in practice. I was ready. And then I found out Chris was sick. It was a relief that I was in the semifinals, but on the other hand that's not how I wanted to get there. I would rather have lost fighting on the court than win this way."

Austin, the 18-year-old Californian who is ranked No. 2 in the world, had expected a much sterner test from Mandlikova, the 18-year-old Czech who is ranked No. 5. They had played six times previously, beginning with the 1978 Wimbledon Junior final, and Austin had won every time, but all in three sets.

This time Austin got off to an early jump and never let Mandlikova get into the match. She was running like the wind, getting to everything, and hitting her passing shots ferociously.

Mandlikova has the type of game that can trouble Austin, but she has to play it well. Last night, in the first set, she was changing pace smartly, jerking Austin around the court, creating openings, but then almost invariably making errors instead of hitting winners.

She was able to draw Austin to the net with some short soft shots but Austin -- primarily a baseliner in the Evert mold -- didn't miss a volley. This seemed to dishearten Mandlikova, as did Austin's ability to get to balls that seemed out of reach and hit forcing shots off them.

Mandlikova -- tall and athletic, her long brown hair encased in a red, Indian-style bandana -- showed her immense talent only in the briefest of glimpses. Occasionally she would wallop a marvelous forehand return winner, or coax a drop volley over the net with the deftest of touch, or change the tempo of a rally with her exquisite variety of shots. But on this night the lovely shots were few and far between.

"In the first set, I played very bad," she said. "She hit the ball very early, very deep, and my serve wasn't very good." At the start of the match, Mandlikova was mumbling under her breath in Czech, but by the end she was so thoroughly whipped that she made her asides in English. Just to practice, perhaps.

Austin was the player of the day, but the biggest heart belonged to little Jaeger, a 5-2, 100-pound kid with an enormous heart and tireless legs. Her classes at Adlai E. Stevenson High in Prairie View, Ill., resumed this week, following Christmas vacation, but she wasn't ready to go home.

Ruzici led, 5-1, 0-15, on Jaeger's serve in the final set, when Jaeger ran off 11 unanswered points to scratch back to 4-5. Ruzici served for the match again and got to 40-30 -- match point -- but then strangely forget the tactic that had gotten her into winning position.

Throughout the match, the lithe, 25-year-old Romanian had won important points by angling soft slices and dinks wide and short to Jaeger's two-fisted backhand, forcing errors or at least opening up the court. On match point, she had an opportunity to do this again, but played too safely and netted a weak backhand. Then she thumped a forehand wide and netted another terrible backhand, and Jaeger was even at 5-5.