John Thompson, the Georgetown basketball coach, wants to find out quickly how many of his reserves he can count on this season. So last night, against Yugoslavia Cibona, he played his starters just enough to take away a 67-65 victory in an exhibition game at McDonough Arena.

Craig Shelton, the team's superb forward, scored nine of the Hoyas' final 14 points, including two free throws that clinched the victory with 10 seconds remaining. The starting five, good enough to get Georgetown a No. 19 preseason ranking by the Associated Press, played only 10 1/2 of the opening 29 minutes and outscored the Zagreb club team, 28-11.

"A game like this is kind of stupid. You kow what Craig Shelton can do and you know what John Duren can do. Yet you still want to win." Thompson said. "Last year, we didn't use many players. I feel it's important to have confidence in the kids who didn't play.

"I want to be able to play eight or nine men this season," he said. "But I'm not going to use them if they're not going to be able to do the job."

Thompson started the team that likely will open against Bowie State Dec. 1, with Maryland looming on Dec. 5. The GU lineup includes four starters from the final game of last year's 24-5 season -- center Ed Spriggs, guard Eric (Sleepy) Floyd, Shelton and Duren.The other starter is sophomore Eric Smith, who backed Steve Martin last year.

The big thing Thompson said he was looking for was the team's "personality," in terms of "when things are going well, will they relax; when going bad, will they keep their poise?" He also is hopeful 7-foot center Mike Frazier can lose some weight and get in shape to back up Spriggs.

The main problem with the reserves last night was a lack of offense and Thompson felt that contributed to a less-than-spectacular defensive effort that left Cibona's excellent outside shooters with open jumpers they converted. Srebrenko Despot scored 22 points for Cibona, now 5-3 in its American tour.

This is not the same team that Maryland defeated recently. The Cibona club team has six players who compete on Yugoslavia's national teams. Cibona is a food-processing company.