Craig Shelton, the most highly sought basketball recruit in coach John Thompson's five years at Georgetown University, will probably not play this season because of his lingering knee injury.

Through an ironic twist of NCAA rules which Thompson termed "bassackwards." Shelton will almost certainly lose a year of elegibility, even if he does not play this season.

Shelton, Thompson and Dr. Carl McCartee have met several times ince September to discuss the slow healing of the kneecap which Shelton tore apart last April while jumping. The two halves of the severed patella still have not completely joined, the most recent x-rays show, despite three months in a cast and six months rehabilitations.

Nevertheless, yesterday was the first time Shelton and Thompson met to discuss the possibility the 6-foot-7 power forward, nicknamed Big Sky might sit out the entire year.

"I can't play. I'm running five miles a day and practicing with the team," said Shelton, who still has somewhat restricted agility and cutting ability. "I feel pretty ready. But my opinion about my knee doesn't count. I'll listen to the doctor and coach Thompson."

At this time, both McCartee, who calls the knee "still precarious . . . not completely healed," and Thompson, who says "I refuse to jeopardize Craig's career for a couple of games," agree chances are poor Shelton will improve rapidly enough to play this year.

In fact, even if the knee now showed sudden improvement, Thompson said, it is doubtful he would let Shelton play.

"Why throw him in unprepared and tentative at the end of the year when everybody else is rolling? It might do him psychological harm. I don't want him to destroy himself mentally or physically by coming back too soon," said Thompson.

Nevertheless, the GU coach admits, "We need Craig. He's got it. You can tell from the things he does in practice. Sometimes I have to stop him before he gets carried away. It make me hungry to play him. Even half of Shelton now could do a lot for this team, but I never want to see him learn, but I never want to see him was what made him a great player."

Shelton first suffered a nondisplaced fracture of the right patella in September 1975, which required no surgery. Seven months later, after a senior year in which he led Dunbar to the mythical national high school championship, Shelton split the patella in half along the same basic lateral line as the original fracture. The massive stress of his jumping also separated the supporting knee ligaments.

Shelton, picked to several "dream teams" as one of the nation's top five schoolboys, could lift only five pounds, with his leg when the cast came off after that all-star game injury. Now the leg can hoist 50 pounds. But the healthy leg can lift considerably more. And the right thigh is still slightly atrophied.

"The knee has made fine progress. It looks like the kneecap will make a complete union, and that wasn't always certain," said McCartee. "When the patella bone heals completely it should be as strong or stronger than ever.

"But it's still precarious in the last X-ray," said McCartee. "We can't take the chance, until I can deem there's not much risk. If he were reinjured, you might have to take the lower half of the patella out. You would have to say that would jeopardize his career sooner or later."

Thompson stresses that while he always tends toward "conservatism in things like this," he is particularly cautious in this case because, unlike many lingering, restrictive knee injuries, the promise of complete recovery is still held out for Shelton.

The chances of Shelton's knee being restored are far better than the odds on reclaiming this year of his eligibility.

"I don't think there is any way to salvage the year of eligibility," said NCAA assistant director of enforcement Bill Hunt. "The NCAA has looked specifically at just this sort of problem and it has an official interpretation. That interpretation is: No way and under no circumstances."

Hunt pointed out that if Shelton had been injured after enrolling at GU, rather than before, he would have lost no eligibility.

The complicated rationale for the "double-standard" rule is in part that it helps minimize cheating through fraudulent injuries claimed by colleges who want to redshirt freshmen.

"Most everything about NCAA rules is bass-ackwards," said Thompson. "They're geared toward assuming everyone will cheat at every opportunity. But now it may back fire on someone like Craig who certainly wasn't trying to cheat by hurting himself.

"Maybe Craig would never make use of that fifth year of college and fourth year of eligibility if he had it," said Thompson. "But it would have been a psychological comfort to him to know that he hadn't lost anything because of the injury.

"It's not going to make me play him any faster because I know he's probably going to lose the eligibility. But it does put more pressure on both of us. Now every week you're going to wonder, 'Should we take the chance now.'"