Yes, Hana Mandlikova nodded, what her father had said was true. A slight blush crept over her womanchild face, as if a deep secret had been revealed. Yes, she used to be a bit too concerned with impressing the spectators. Papa had told her it was more important to play winning tennis.

Her father is Vilem Mandlik, twice an Olympic sprinter for Czechoslovakia, now a sportswriter for the Czech army newspaper. Last month he told a visitor to Prague that his daughter, the U.S. Open runner-up and most electrifying young star of women's tennis, had to overcome a tendency to showboat.

"She would play her best tennis for one set or so, and then forget she needs to win the points," he said. "She would start to play nice tennis, spectacular shots, to entertain the audience. I told her, 'I know this is you, but it is foolish to lose the match to please the spectators.'"

Now Mandlikova, 18, the top seed in the $250,000 Colgate Series Championship that begins Wednesday at Capital Centre, was in Washington, getting the lowdown on what her father had said.

"That's right, but I think that was last year," she said. "I hit the ball and looked to see how pretty the shot was, how nice I hit the ball on the line. But not too much anymore." Her blue eyes sparkled, and laughter turned the complexion of her lovely, expressive Slavic face the reddish shade of an apple. "I think I'm changing."

Until mid-1980, Mandlikova was a brilliant but unconsolidated talent, noted for her athleticism, extraordinary range of shots, and unpredictability. For a set or so she could be the best player in the world -- a tall, slender vision dashing to the net, doing extraordinary things. Then suddenly, mysteriously, the exquisite touch would disappear. The powerful serve would misfire. The sublime became ridiculous. She was an artist inspired by a fickle muse.

The evidence kept piling up. She took sets from Chris Evert Lloyd in the Italian and French Open semifinals, led Tracy Austin, 6-1, 3-0, at Eastbourne, England, led Evonne Goolagong Cawley at Wimbledon, 6-3, 3-1, 40-15, and lost them all.

This happened so often that the top players came to expect her to soar, then crash in flames. Physically and technically, it was said, she has it all -- superb legs, reflexes, racket control, strokes. But in the head, opinion said, she is not a champion. She can't finish a match.

That assessment has changed in the past five months. Since August, when she beat expatriate Czech Martina Navratilova, her onetime idol, and cleared an important psychological hurdle, she has been a different player. Even though she lost to Evert two weeks later in the final of the U.S. Open after winning the first set, she has since demonstrated the ability to close out matches, winning five more tournaments and climbing to No. 5 in the computerized world rankings.

In Atlanta this fall, she finally beat Evert. By winning four of six tournaments down the home stretch, she topped the point standings for the worldwide Colgate Series of 39 tournaments, earning a $115,000 prize and the top seeding in this week's playoff for the top eight finishers.

The process started earlier -- right after Wimbledon, when she enlisted Dutchwoman Betty Stove as her coach and confidante -- but Mandlikova's big breakthrough came that week before the U.S. Open, when she beat Navratilova and then 15-year-old Andrea Jaeger to win a tournament in Mahwah, N.J.

"That was the first time I beat Martina. After losing the second set, 2-6, I won the third, 6-4," said Mandlikova, who has a graphic memory for match details. "I think this was a very important match for me, which gave me confidence, because I started to know I could win a match in three sets and beat very good players."

Six years younger than Navratilova, Mandlikova never played or practiced against her idol in Czechoslovakia, but she was a ballgirl for her in a club match at the Sparta Club when Navratilova was an 18-year-old.

"She and another Czech girl, Renata Tomanova, were playing, and they asked me who I wanted to pick up the balls for. I said, 'I like Martina's style. I want to pick up the balls for her, because I like the way she's playing,'" Mandlikova said. ". . . It was not really a dream, but always I was thinking about when I would beat Martina. Always."

Mandlikova chafes now when reminded of her past reputation for unraveling."I think that was before Wimbledon," she said. "After Wimbledon, I haven't any match like this. Goolagong at Wimbledon was the last one."

Shortly thereafter she hooked up with Stove, 35, the 1977 Wimbledon runner-up, who is respected, worldly, experienced, tactically astute, and still very much on the scene, good enough in doubles yet to make the Colgate Series Championships alongside Pam Shriver.

"I think the first point -- very important point -- is when I started working with Betty Stove, she told me: 'You must improve your patience and your concentration in the matches.' So we were working very hard on that, and for me, this is the way to go up," said Mandlikova.

Stove brought order and intensity to Mandlikova's workouts, focusing them on specific objectives, stressing the need to concentrate on every ball and think in practice as she would in a big match.

Stove acts as a surrogate conscience, quietly imposing discipline, reminding Mandlikova that serious attention to preparation -- even such seemingly trivial details as when and what to eat, and when to do the laundry -- is important. She is also a sounding board for tactics, and a friendly companion who has made the often lonely and tedious life of the circuit easier. c

"Before I never talked to anybody about strategy, but Betty has been traveling a long time, 20 years, and she knows how to play the others," Mandlikova said.

"Also, I don't like to travel alone. Before, I was not so comfortable on the circuit because I didn't speak very well English, and if you go somewhere the first time and see something new, you are a little bit frightened.

"In Las Vegas, I lost the final to Andrea Jaeger" -- her opening night opponent here, Wednesday at 7 -- "and I was very tired because we came from Tokyo before, and discouraged because I lost. Betty said, 'Come on, it doesn't matter, let's go swimming.' I still had on my skirt and T-shirt from the match, but we jumped into the pool. I forgot for a minute that I lost the match, and that's very important. She knows me very well."

Helpful as Stove has been, someone who knows Hana even better put her on the path to the top, and has helped her along. It was from Vilem Mandlik, 1956 and 1960 Olympian, that Hana inherited her speed and sprinter's physique, but he gave her much more than good athletic genes.

It was Mandlik who carved her a wood paddle -- a scaled-down replica of a racket, without strings, of the type long used by youngsters starting out in tennis in Czechoslovakia -- and gave it to her when she was 9. She played with it for a month, hitting imaginary balls on an imaginary court in front of a mirror, practicing the strokes she now hits so stylishly.

After four weeks she was ready for a real racket, and Mandlik hit real tennis balls with her for the first time. The strokes were already pretty, he recalls, proudly showing the scar where he gashed his left thumb while making her original paddle.

Papa Mandlik, now 43, who encouraged the net-rushing style that came naturally to her, told her, "Hana, if you can hit 200 volleys without letting the ball hit the ground, I will buy you ice cream."

He reassured her when this aggressive style did not bring immediate good results in junior tournaments. He told her it takes longer for an attacking game to jell, that she would grow into the style, and he was right.

"When I lost some matches, he said, 'Tomorrow morning you come back again, and just keep playing; you will win,'" remembered Mandlikova, who never won a national tournament in any age group until last year. "I wanted to be very good player, and when I got disappointed he picked me up."

Her father worked with her and other young Czechoslovak players, on the track at Prague's Red Star Club, teaching them exercises to improve their speed, strength and agility.

Mandlik, who was so happy when his daughter reached the final of the U.S. Open that he and his wife drank three bottles of champagne, looks lovingly at his daughter and sees himself, in temperament as well as athletic ability.

"She is stubborn, with a strong will," he said. "I was the same way. My father and I loved each other a lot, but we were always fighting. If he told me I must do something, it was 100 percent sure I would do the opposite. It was the same with Hana, but maybe I knew a little more psychology. I knew if I told her, 'Hana, you can't go skiing, you might get hurt for tennis,' she would be on the slopes immediately. So I told her coach instead, and he told her it was too dangerous to ski, and she would listen to him. I gave my advice through others."

Mandlikova knows this is true. "That's right, that's right," she said, blushing again. "We are both the same, and we are sometimes fighting, but now it is better. I am older, and we understand each other. Anyway, I always believed what he said even if I didn't want him to know."

Most of all, she took to heart his constant admonition that no matter how gifted she was, she had to keep working hard to improve, and concentrate on winning, not just on looking good on the court. He taught her that nothing comes without hard work, training, and sacrifice.

"You know, many times people say to me, 'You are a talented player, a natural player,'" Mandlikova says now, "and I say, 'All right, I am talented, but that is not all. If you have talent, you must give everything to be the best. You must work, to make yourself strong. I am more stronger now, and stronger in the head.'"

Yes, she nodded again, what her father said was true. People pay attention to champions, not flashy losers. CAPTION: Picture, An August victory over former idol Martina Navratilova has helped the No. 1 seed in the $250,000 Colgate Series become a more confident player. By M. C. Valada for The Washington Post