When Mychal Thompson was the star center for the University of Minnesota; the general manager of the Washington Bullets, Bob Ferry, returned from a scouting trip and told Coach Dick Motta he had just seen a great future pro.

"Another Alvan Adams," said Ferry.

After Thompson scored 29 points and grabbed 14 rebounds against the Bullets two weeks ago, Ferry slightly changed his opinion of the Portland Trail Blazer rookie.

"Still another Alvan Adams," said Ferry. "But with a lot of Elvin Hayes mixed in."

"That's right," Hayes said yesterday. "I see a whole lot of me in him.

"Maybe," he added with a slight smile, "that's why he is so good."

The pairing of Thompson against Hayes tonight at 8 o'clock in Capital Centre represents an opportunity to witness what can be called a Changing of the Forward in the NBA.

Hayes is the reigning premier big forward in the league, a player blessed with a combination of quickness, strength, jumping ability, endurance and shooting touch that perhaps has yet to be equaled at the position.

Although Hayes kiddingly says he will not retire until he is 50, he is 33 and beginning the descent of his career, which has spanned almost 11 proseasons.

In Thompson, Hayes says he sees someone "who has the ability to be as good as he wants," to be as good as, yes, Hayes. At 6-foot-10, Thompson is an inch taller than Hayes but weighs 10 pounds less and is not nearly as strong or as aggressive. He is a scoring machine, much as Hayes can be, runs the court excellently, can block shots and play defense. Already, he is a better passer than Hayes.

"The first thing you notice about him," said Ferry, "obviously is his ability to score. He has confidence when he gets the ball and he can put it in for you, from a lot of places and very consistently.

"But there is more to his game than shooting. People questioned his intensity and I think that still might be a problem. He might have a tendency to go in peaks and valleys, like he did in college.

"But he is a great passer. That's why I look at him as another Alvin Adams. If you double-team him, he won't force it . He'll fing the open man and drop it off.

That's what makes him even more dangerous.

"He is so fluid, he moves so well. He isn't the same as Elvin as far as being physical. He swon't fight pressure; instead he flows or glides. That's why maybe he doesn't look like he is always playing at top speed. He is deceiving because basketball comes so easy to him."

ferry like Thompson so much that he wanted to draft him two years ago, when the Minnesota All-American was seriously contemplating giving up his senior year of college and turning pro.

In the draft, the Bullets had the fourth pick, which proved to be one too low. Feery and Motta journeyed to Minnesota and made sure Thompson knew how strongly they felt about him, but the fear that Buffalo, which had the No. 3 selection, would take him prompted Thompson to remain at Minnesota.

"There were a lot of things we could have done to get a higher pick," said Ferry, "but I guess he didn't want to take a chance on something getting messed up. He passes so well he would have fit into our offense and he is just another versatile player for us to work with."

Portland thought enough of Thompson to give up a No. 1 draft pick and guard Johnny Davis to Indiana to guarantee the Trail Blazers could select him first in last June's draft. Thompson had expected to back up both Bill Walton and Maurice Lucas, but with both of those stars sidelined with injuries at the start of the season, he has emerged as the club's No. 2 scorer behind center Tom Owens.

"I'm still learning from game to game and team to team," said Thompson. "One night I'm guarding Elvin Hayes, the next George McGinnis.I have to keep asking what I should do against these guys."

Hayes didn't ask anyone about Thompson when the Bullets faced the Trail Blazers in Portland two weeks ago, and it was an evening of enlightment for Hayes. If he laid off Thompson, the rookie quicly put up a jumper. If he got too close, Thompson drove to the basket. Thompson also was involved in a handful of Portland fast breaks ending a couple of them with Hayes-like dunks.

"I never could pick up his style," said Hayes, who had eight points and 15 rebounds. "He did enough different things to keep me guessing. He can do a lot - go inside, outside, down the middle. He really surprised me. I had never seen him play before and you just have to feel your way in a situation like that.

"He makes some of the same moves that I have and he can hit on a turnaround jumper, like I can. I think it's harder covering a guy who does what you can do. You don't expect it."

Tonight should be a better test of how well Thompson has developed as a pro. Hayes says he should be a wiser defender "and not get fooled as much by what he can do." The rookie will be guarded harder and he won't be on his home court, where partisan cheers often can induce superio effects.

Hayes, of course, has dealt with other challengers in the past, including Portland's veteran big forward, Lucas. But he admits few have treated him with less respect than Thompson.

"He never hesitated," said Hayes. "The man got the ball and he shot it. You'd think he'd go easier on an old man like me.

"I've seen where he has had a couple of low-scoring nights and some big nights. The pros are different. you have to get used to the grind and the routien. Then he'll become more consistent.

"But like Bill Russell always told me," Hayes said slowly, "there is always another night for everyone. You get beat once, you try again.

"That's something I'm sure Mychal Thompson is learning, too."