It was only last summer that Bob Knight, the lovable Indiana University basketball coach, said Ralph Sampson wasn't ready for pro ball. Not only that, said the master, Sampson wasn't even ready for college ball. This, of course, is praise from Knight, who condemns only those in whom he sees potential. He calls it motivation.

Even as Knight was questioning Sampson's ability, the coach kept him in the United States' Pan American Games team while leaving off a fellow named Darrel Griffith, who turned out to be a pretty fair player this college season.

And now Ralph Sampson is ready for the pros. At least, Red Auerbach thinks so. The Celtic general manager is to meet with Sampson's parents and coaches today in Harrisonburg, Va. If everything goes the way it ought to, the University of Virginia will be looking for a new center soon because Sampson, after one year in college, will become a professional.

First, Sampson needs to see the color of the Celtics' money. If the Celtics are coming with, say, a $1.5 million deal, then Sampson, in all his 19-year-old wisdom, should ask the most important question, that being, "Please, Mr. Auerbach, can I sit on the bench for a couple years?"

Both the money and the need to ride the bench for two seasons are matters of security.

As good at Sampson is, he is going to get better. A teen-ager 7-foot-4 with an outside shot and a behind-the-back dribble will be worth more than $1.5 million three years from now. Only a serious injury would

If Ralph Sampson is worth $1 million now -- that's the magic figure at which his college coach, Terry Holland, says he would say, "Take it and run, Ralph" -- what would Sampson command if he dominated the Atlantic Coast Conference for three seasons?

The need to sit on the bench seems a paradox. Moses Malone earns his million by getting seventy-eleven rebounds a night. For Sampson, though the two years on the bench are important for both his physical and psychological growth.

He is very thin. He needs 25 or 35 pounds of muscle to survive inside in the NBA. That strength will come with age and with working out with weights. Even during the relatively short college season -- 35 games, not the 82 of the pros -- Sampson was ill more than once, worn out by the work. He never dominated ACC teams close to the hoop, where a 7-4 center must play to earn his pay.

Psychologically, Sampson needs to sit on an NBA bench. Buck Williams, a strong player, couldn't lift the necklaces Darryl Dawkins wears. One hesitates to imagine the cavity in Sampson's chest should Wes Unseld give him an introductory love tap in jostling for rebounding position.

Sampson is an extraordinary talent. There will come a day when Darryl Dawkins will grow faint at the prospect of facing the kid. But not now. By playing part time for a good team such as the Celtics, and playing behind a veteran center such as Dave Cowens, Sampson can learn what the NBA is about without carrying the heavy burden of victory all alone.

Where he, for example, to wait another year to go into the NBA undergraduate draft, there is the likelihood he would be chosen by the new Dallas expansion franchise. There the psychological load would be backbreaking. He would be the whole show. Victory of defeat would hinge on his every performance. As Elvin Hayes learned in his early days with new Houston and San Diego teams, such expectations are impossible to fulfill.

For $1.5 million, for a seat on the Celtics' bench, for personal instruction from Dave Cowens -- for escape from Dallas, Ralph Sampson ought to turn pro today.

And why not? Romantics say the kid isn't wise enough to handle the pressures of the real world, he needs the college education, he needs to meet people, he needs to know that there is poetry in this world as well as dollar signs. These romantics, helpless souls, see the Celtics as predators stealing Sampson from his future.

They don't realize that the Celtics are Ralph Sampson's future.

Isadora Duncan, the dancer, once proposed marriage to George Bernard Shaw, the playwright. She said such a union would produce a beautiful genius. "but what," Shaw said to Isadora, "if the poor thing had my body and your brain?"

At birth, one suspects, the doctor spanked Sampson and sent him to midcourt for a jump ball. The kid is the ultimate player, a skyscraper who can do little-man things. Whoever mixed the genes mixed them well, for in Sampson both the body and the brain were made for basketball. He decided ages ago -- well, three years is ages when you're 19 -- he would be an NBA player.

First, though, he would stop off at Virginia for two years at the most, he said. It's a deal, Virginia said, ackknowledging the obvious that big-time college basketball is big business that depends on selling tickets and producing donations.

If Ralph Sampson wants to play for only two years, fine. For more than 100 years Americans have proved they want colleges to provide athletic entertainment. And it is just as properly a function of our colleges in this sports-crazy country to provde young athletes with training for professional sports careers as it is to prepare budding poets for a life's wrestle with the muses.

College gets us ready for our life's work. Sampson's work is basketball. He said he had no academic ambitions, just as, one supposes, Einstein had no mad desire to slam dunk. So as long as Sampson can obtain both physical and psychological security right now, why wait? Who among us would turn down $1 million at 19 to do what we've dreamed of for ages?

One thing more. Of the 242 active players in the NBA, how many do you suppose quit college early to turn pro?

Julius Erving did. Magic Johnson did. Moses Malone never went to college at all, nor did Dawkins. Adrian Dantley left Notre Dame early, George Gervin left Eastern Michigan, Bob McAdoo quit North Carolina.

Not a bad first seven men on our All-Born-to-Slam-Drunk team. And they are just the start. Of 242 NBA players, 27 quit college early to turn pro. a