A quick reading of tea leaves tells us Ivan Lendl will win this U.S. Open tennis tournament, beating Jimmy Connors in the final. First, Lendl will win a Saturday semifinal against John McEnroe, whom he has beaten five straight times. And Connors will advance with a struggling victory over Guillermo Vilas.

Guillermo Vilas?

Casual observers of the tennis scene may have forgotten the Argentine poet. Wasn't it 1977 when he won everything except Wimbledon? He wore his hair shoulder length, reined in by a headband, and he had a coach named Ion Tiriac, a Romanian whose heavy brow, hanging mustache and narrow-set eyes suggested sinister deeds aborning.

No. 2 in the world only five summers ago, Vilas long has been eclipsed. Because his relentless base line game was built on clay and resisted his best efforts to make it over, Vilas never matched Connors and Borg and McEnroe. He foundered each summer on Wimbledon's grass, and after the U.S. Open left clay in '78 he never reached its semifinals again -- until now.

With Argentina at war with the United Kingdom this summer, Vilas chose not to play at Wimbledon in June. He had reached the final of the French Open the month before, yet we remember him there only as a footnote in the Mats Wilander fable.

As a matter of fact, Vilas has played superbly this year. In 14 tournaments, he has won seven times and been runner-up two other times. But it is of little note to beat Jimmy Connors twice in finals if those victories come at Rotterdam and Madrid in March. About all that will get you, as readers of Paris Match magazine know, is a picture of you and your girlfriend, Princess Caroline of Monaco, taking the sun au naturel.

Vilas is quick to take exception to the idea that by reaching the semifinals here, he has accomplished anything of a comeback.

"In my entire career," he said at a press conference this week, "my lowest ranking was seventh. And that for three weeks. I never had a bad year. Last year is the only year I did not win a major tournament, yes, but I was in 12 finals and won three tournaments. So."

He is testy, too, on whether or not he can win big tournaments on surfaces other than the clay of his youth.

"Yes, I like clay more than any surface, because this is what I grew up with. But I believe that all players should play all surfaces, all tournaments, to be the best. And it hurt me to miss Wimbledon when I was in the middle of a very good time. I was playing very well."

His work this U.S. Open fortnight is without fault. Down two sets to none against the power-hitting Steve Denton, Vilas found a way back for a dramatic five-set victory that included a fourth-set tie breaker.

"I had to go for more winners after losing the first two sets," Vilas said. "I was playing safe so I started playing a little more percentage . . . I feel I was lucky, but to win you have to be lucky. I earned it, under the pressure. I went for it."

One of Vilas' stratagems against a man serving thunderbolts on a hard surface was to take his serve standing nearly against the grandstand wall.

"I would have stood further back," Vilas said, "except they told me there was a highway back there."

Then, serving well and crashing his topspin backhand into unreachable corners, Vilas was overwhelming in his 6-2, 6-1, 6-3 quarterfinal victory over Tom Gullikson Thursday night.

So overwhelming, it seemed, that casual observers concluded that the Guillermo Vilas of '77 never really went away. He is 5-4 lifetime against Connors, having won their last two meetings this March. And here he is today, 30 years old, a published poet in Argentina, a movie actor, born to a lawyer's family privilege and now a man with a princess on his arm. Here is Vilas still with the long hair in its headband, still with the heavy topspin backhand, still with the maniacal fetish for eight-hour workouts that include an hour's worth of nothing but footwork.

And still with Ion Tiriac, brooding.

Or is Tiriac signaling?

It is against the rules of tennis for players to take signals from coaches at courtside. Few coaches are more dominant than Tiriac, for instance, and the Argentine poet on the court often seems little more than the dancing puppet of a Romanian Svengali.

Early in the Gullikson match the other night, Vilas left his change-ends chair and sprinted to Tiriac's place in the bleachers. They talked. One supposes they talked about tennis tactics, and not the color of Caroline's hair, but Gullikson didn't complain.

Throughout the match, Tiriac was very busy with his hands. Some cynics suggested these were signals to Vilas dictating tactics.

When a reporter said to Tiriac this afternoon that some people were upset with what they thought were hand signals, he said, "They are upset for the last nine years."

Did he give signals?

"Maybe," Tiriac said. "I don't remember."

His mustache never looked more sinister.