They are supposed to come along once every 10 years or so, the freshmen who can really make an impact on the game of basketball.

Well, we are in the presence of such a one in Earvin Johnson of Michigan State. He could very well be the ultimate basketball player, the prototype player of the future.

Johnson is only 18 years old and while it may be early to compare him with Oscar Robertson and Pete Maravich, Johnson definitely has to been seen to be believed. As they say on the playground, he is the truth.

Johnson is 6 feet and 8 and a natural guard - not just a quick forward who can handle the ball, but a legitimate ball-handling whiz who can dominate a game like a noncenter since the Big O himself.

"They always say you start your program with a center, but we have a 6-8 guard who can play anywhere," said Michigan State coach Jud Heathcote. "Earvin is as good as any guard at bringing the ball up and when he goes inside, he's as good as any forward. He has come in and really taken over.

"People made a big thing out of Cornbread Maxwell bringing the ball upcourt last year and said he was such a great ball-handler.Well, hell, he was bringing it up against big, slow centers. Earvin does it against real pressing guards."

Johnson is the major reason the Spartans, 10-17 last year, are 18-4 now and share first place in the Big Ten.

Johnson is third in the conference in scoring with a 19.3 average, first in assists with 6.4 a game, fifth in rebounding with 8.6 a game and is shooting 50 per cent from the field and 83 percent from the foul line.

"He is the best player I've seen since Oscar," said Purdue Coach Fred Schaus, who has been coaching 18 years in the National BasketbalI Association and the colleges. "I have never seen a 6-8 man who can put the ball on the floor and handle it like Earvin can. He is a real guard, a complete player. I tell you, he is phenomenal. He's got a perfect 6-8 body for this game.

Johnson is not the only member of the class of '81 who has already made his mark. This is an exceptional year for freshmen basketball players around the country.

Darnell Valentine, a 6-2 guard who leads the Big Eight in steals and assists, has already led Kansas to the conference title, and 6-11 Herb Williams has helped make Ohio State a winner again.

Mike McGee at Michigan; Jay Vincent, a teammate of Johnson at Michigan State, and Ray Tolbert at Indiana have helped strengthen the Big Ten overall.And Kelly Tripucka has helped keep Notre Dame going strong.

In the Atlantic Coast Conference, Gene Banks of Duke, Albert King of Maryland and Jeff Lamp of Virginia have blossomed.

Jeff Ruland, a 6-10, 240-pound center for Iona, N.Y., is averaging 21.1 points and 12 rebounds and is shooting 59 percent from the field.

Out west, 6-4 1/2 guard Danny Ainge is scoring 21.8 points a game for Brigham Young and Cliff Robinson of Southern California is leading the Pacific-Eight in scoring at 18.9. He's also averaging 9.9 rebounds.

Robinson, a 6-10, 190-pound leaper, had 11 dunks in two games last week.

"They weren't dunks on breakaways, either," said USC Coach Bob Boyd, "but quick dunks against set defenses."

But Johnson is the main man.

In addition to his wondrous basketball skills, he posted a 3.4 grade-point average in his first semester at Michigan State. He is an outgoing, easy-talking young man who is a student of the game and just as comfortable talking about the sport as playing it.

He is friendly with the opposition, invariably visiting before, during and after the games.

It is a practice of his to give the officials a congratulatory pat on the rump after the game - win or lose.

When it comes to his own team, Johnson says, "I try to be our ringleader and fire us up." He usually does it.He gets his biggest thrill from his clever passing.

He is not exceedingly flashy. Seldom does he throw the behind-the-back, between-the-legs job, but he has such great court vision that it seems he always sees the open man and somehow gets the ball to him.

Like all great passers, Johnson has a problem in that his teammates aren't always ready to receive his deliveries. So a lot of turnovers occur.

The impact that Johnson could eventually have on the sport is dizzying. The best way to describe him is a combination of Maravich and George Gervin.

Gervin is a 6-9 guard for the San Antonio Spurs, and the second-leading scorer in the NBA. But he is almost exclusively a scorer and not a ball-handler or passer. Maravich is the best ballhandler-scorer in the game. Picture those two as one, and you have Earvin Johnson.

Johnson, who went to high school in Lansing, Mich., narrowed his choices early to Michigan and Michigan State.

He says Michigan had a lot more to offer, but he chose Michigan State "because I like the underdog. Every team I ever played on was not supposed to win," he said. "Even when I go to the playground, I don't pick the best players. I pick the players who want to work hard."

Things just wouldn't be right of Johnson didn't have a nickname or two. One of them is Odi, after Idi Amin of Uganda, because, like Amin, Johnson can do anything he pleases and has more medals than he knows what to do with.

The one he answers to most often however, is Magic. After a recent game, the Detroit Free Press even listed him in the box score simply as Magic.

What does Johnson think of his own game?

"I need to improve my defense," he said. "I'm getting better, though. I slide through picks better than I used to. I could improve all areas, I guess. Everybody's game could use a little touching up. Even mine."