The final pages of the latest chapter of one of the great Horatio Alger stories start turning at RFK Stadium Saturday at 8 o'clock when Pele and the Cosmos take on the struggling, demoralized Washington Diplomats.

It will end the season for the Dips and will be the last regular-season game in the North American Soccer League for the Black Pearl, who only has the playoffs before him, and an Oct. 1 exhibition in which he will play one half each for the only two teams that have employed him. The Cosmos and Santos of Brazil.

"Well I think maybe I'm going to play some exhibitions," Pele said in the locker room after The Cosmos heat the Bicentennials, 3-1, Sunday.

"I've got invitations to play in England, South Africa and Brazil and maybe I'll stay with soccer this way, but not so much professionally," he said.

It will be hard to think of Pele not being an active player, although he was retired between October, 1974, and June, 1975, when he made his debut with The Cosmos. There is something about the man, a childlike quality, that only someone making millions playing a child's game can have.

The game has started to become work for the aging start, but the child in him still is evident when he or a teammate scores a goal: a capriole with his first clenced upright ends as he hugs a teammate or tumbles on the ground, while the crowd - friend or foe - takes up the universally known chant; "Pe-le, Pe-le, Pe-le?"

Pele was born to play futebol . It started nearly 37 year ago when Edson Avantes do Nascimento was born in an obscure town called Tres Coracoes in the Brazilian state of Manas Gerais, some 150 miles northeast of Rio. His father was an above-average minor-league soccer plays.

He has taken his artistry to some 140 countries, and has become one of the world's most recognized faces.

Pele was revealed to the world as a 17-year-old leading the Brazilian national learn to its first World Cup championship in Sweden in 1958. Brazil repeated in Chile in 1952, but Pele missed the last four contests, having suffered a thigh pull against Czecholsovakia.

In 1966, Pele was brutally fouled in a first-round World Cup match against Portugal in England, which spelled Brazil's elimination and led to an eventual rule change in international soccer, allowing limited subsitution for the first time.

Pele came back in 1970, as Brazil won its third title. In the time between Pele's two championship finals, he had become a living legend, and his club, Santos FC, had won several South American and world club titles.

It was little wonder then that the soccer world was shocked when "O Mais Grande" (The Greatest) came out of comfortable retirement to tread the uncertain waters of the North American Soccer League. What did he have to gain?

Money. A total of $4.5 million to play and be merchandised for three years and about half that much again to do public relations for The Cosmos and the Warner Communications entertainment conglomerate for three more years. That kind of money helped him recoup losses incurred in bad business ventures back home, and assured the good life for Pele and his family - wife Rose, daughter Kelly Christine, 10, and son Edson, 7.

But Pele had other tempting financial offers - so why come to soccer wasteland U.S.A.? He explains his missionary zeal:

"I looked around the world and saw that America is such a great country, but is the only country where soccer is not popular, and thought I can help make it more popular."

Even at the price. The Cosmos got a bargain. Former club president Clive Toye, who convinced Pele to come, said in an interview earlier this season that Pele "gave this franchise and the league as a whole instant credibility."

The NASL became legitimate in the eyes of the world, and more important, in the New York press. The league and the team have exploited Pele's worth to the hilt, alienating only the most hard-boiled critics who recognize that Pele vintage 1977 is not the same as vintage 1970 or 1958.

But the league's attendance has gone up (about 30 per cent this year) and even The Cosmos have begun to draw at home. Warner Communications boss Steven J. Ross said this week the club will be in black ink by next year.

"The key was not when we drew 62,000 against Tampa Bay, but when we drew over 34,000 (July 6 against San Jose) against a mediocre team on a rainy night when the Yankees were postponed and our game was on delayed home TV," Ross said.

Sunday 48,000 came to see The Cosmos methodically pick apart the lowly Bicentennials, as Pele got his 12th goal of the season.

Pele, who says he now will be a "consultant" to the Cosmos, has been the ultimate public relations man. He is always willing to give an interview if you can get to him, and he is willing to travel.His manner is humble but sincere. He generally has praise for the opposition, loves children and has worked on his English to the point that he now rarely needs a translator for postgame interviews.

Bringing him to America was a calculated risk, for there is so much hoopla surrounding Pele that American fans tend to forget anyone else plays in the NASI. But Pele has attracted other superstars, and there are four other players on The Cosmos alone who have played in World Cup final rounds either in 1970 or 1974, including the captains of the last two champions: Carlos Alberto of Brazil (1970) and Franz Beckenbauer of Germany (1974).

League officials see this and attendance figures in other, primarily western, cities as indications that American pro soccer will survive.

It was all made possible by the living legend who took on the odds in The Big Apple, where many a would-be legend has bit the dust.

"It was tough in the beginning, you know, when I came for that first season." Pele said, "I had a little problem with communication and it was the first time playing on AstroTurf - all in all, it was kind of rough.

"But this season, playing with Beckenbauer and the other stars, that's been nice, real nice. That means a lot to me and to soccer, too."