For nearly four hours at the U.S. Open today, it seemed that the first men's semifinal match on center court would mirror the signs in the boutiques: cash only, no checks.

In the end, however, the Czech in question -- Ivan Lendl -- cleared while Pat Cash was the chap whose account came back marked "insufficient funds."

In a five-set match that was as full of thrills and chills as it was of chokes and jokes, Lendl reached the final here for the third straight year with a 3-6, 6-3, 6-4, 6-7 (5-7), 7-6 (7-4) escape that may change both his image and his Grand Slam fortunes.

This was the day when Lendl, who is known in this tough town as a guy who gags on pressure, finally got his tennis books into the black. Perhaps, a day or a decade from now, we'll call this one of the turning points in Lendl's career -- the moment when a tin man found his heart.

Deep in the fifth set, Lendl seemed doomed to another of his embarrassments in the U.S. Open -- the tournament that seems to expose Lendl's competitive flaws like an X-ray machine for the tennis soul.

The 24-year-old Czech with the fabulous strokes and the brooding manner had not only blown a 2-1 lead in sets over the 19-year-old Cash, but had tossed away a match point in the fifth set, as well.

Now, with Cash serving for the match, Lendl had hit rock bottom. Almost always in these situations in the past, he had folded his tent and sulked away defeated.

This time, Lendl looked inside himself and found a new and simple composition of feeling.

"I thought, 'Just try. Maybe you will get lucky and win,' " he said.

When, minutes later, Cash had another match point, Lendl flipped a great lob over his opponent's head to dodge defeat.

When that game ended, this day's indelible moment arrived. That's when Lendl did what countless tennis fans have hoped he would do for seven years.

He reacted from the gut. Lendl pumped his fist, for all the world looking like his antithesis, Jimmy Connors, the street fighter who once called Lendl "a chicken."

Cash, who is a hot-tempered brawler and all-around pretty hard case, took the gesture wrong. Or, perhaps, took it just as it was intended.

He pointed his finger at Lendl as though to say, "Don't you show me up or we'll play some Australian rules tennis."

Lendl, the man who solves the Rubik's Cube in seconds, learns languages in months and sometimes seems to have an Apple computer for a brain, glared back at Cash and pointed his finger right back.

"Don't you yell at me," Lendl yelled at the muscular Cash.

After the match, Cash said that he was really pointing and yelling at a linesman. Maybe so, although it didn't look that way. What matters is that Lendl, in a moment when he thought his heart and guts were being challenged, reacted with competitive fire.

From that moment, Lendl seemed almost fated to win. When he fell behind, 3-2, in the final-set tie breaker, with Cash holding two serves in hand, Lendl still did not seem demoralized. Rather, he kept blistering shots at Cash's feet as he charged the net, or else flicked those topspin lobs over his head.

To be honest, let's admit that Lendl hit countless embarrassing shots in this 3-hour 39-minute match that often threatened to degenerate into a comedy of errors. But what matters is that, while he may have stunk out the joint at times, Lendl never quit.

When Lendl had a match point in his hands in the fifth set and blew it with a backhand into the net, he didn't come unglued. He didn't paw the ground and pity himself as he has in past performances, both here and at the Masters that have rightfully earned him "Ivan the Choker" headlines in the tabloids.

"They say I never can come back in a match," Lendl said afterward. "I came back from two sets and a match point against Vitas Gerulaitis in the Masters. I came back from two sets down to McEnroe in the French Open this year. But some people will always say that, no matter what I do. I could come back from 0-6, 0-6, 0-5, 0-40 and it will not stop them . . . you must win for yourself, more than to silence your critics."

If Lendl made a few friends for himself and for tennis this afternoon, Cash, who also reached the semifinals at Wimbledon this year, may have damaged his chances to have himself painted as the next potential superstar of tennis.

He lived up to his reputation for grouchy arrogance with a postmatch performance that rivaled the worst of McEnroe for teen-age boorishness.

Asked at the press conference to comment on his finger-pointing episode with Lendl, Cash exploded with a tirade that had the veins in his neck standing at attention. "I can't honestly believe you asked that. We played 4 hours of the most amazing tennis. We just played the most unbelievable match of my life . . . the most exciting tennis New York has ever seen, and that's the first question I get . . . I was just yelling because I was disappointed . . . Your ethics are unbelievable."

As unbelievable as Cash's manners?

When you're one of the most frequently fined player on tour, when you point fingers and scream during matches and when you walk off, snubbing a TV interview, and fire your racket at the spectators, you're fair game for questions.

Someday, at the U.S. Open or Wimbledon, Cash may reach a moment when he learns to restrain and channel his rage just as, today, the placid Lendl learned how to release his fury.

Then, Cash may be ready to break camp for a climb to the top of the tennis mountain. Whether Lendl is now ready to make that ascent is a question for another day.

Perhaps even Sunday.