By the time Ralph Sampson ended his block-and-dunk show tonight, Virginia Tech Coach Charlie Moir could only wonder how it might have been if the 7-foot-4 junior had chosen his college.

Sampson, who was recruited earnestly by VPI, now is making a career of picking on the Gobblers. His 25-point, 21-rebound masterpiece tonight made it easy for third-ranked Virginia to coast to an 80-66 triumph, its seventh straight over the arch-rival Gobblers.

In three games against VPI, Sampson has scored 58 points and gotten 61 rebounds. But never has he been quite as intimidating and quite as in command as in this one, once-beaten Virginia's 22nd win of the season and ninth in a row.

Tech didn't even try to challenge him inside. "To win, we knew we had to shoot well from the outside," Moir said. So the Gobblers kept putting up errant long-range jumpers, Sampson kept rebounding the misses and Virginia, once it settled its offense down, gradually turned the game into a runaway.

Only a poor first half performance by the Cavaliers kept Virginia Tech within range for more than 20 minutes. Virginia committed 11 turnovers in the opening period (the Cavaliers average only nine a game), eliminating chances to make an early scoring run.

But the Cavaliers made their first five shots of the second half, all from the outside, and seven of the initial eight attempts. Tech could only try those woeful jumpers and soon found themsevles down, 47-28, after trailing at intermission by only nine.

"We got impatient and tried to go one-on-one too much," said Moir, whose team shot only 38 percent, 14 below its season norm. "We took some tough shots. If you miss them, you get blown out and that's what happened to us. Our good shooters were taking the shots, they just weren't going in."

Virginia Tech, at 15-5, has a solid record. Yet Virginia was far superior tonight.

And no Cavalier played better than Sampson, the increasingly enthusiastic junior who fell one short of his school rebounding record, despite missing the game's final minutes.

The rare occasions when Virginia Tech tried to maneuver inside were rendered useless by Sampson, who had seven blocks. Once forward Calvin Oldham tried a 15-footer with sampson at least seven feet away. Somehow, Sampson blocked and caught the ball, leaving Oldham shaking his head.

"Ralph," Moir said, "sure looked like he was enjoying himself out there."

Oldham had the thankless task of trying to stop Sampson despite giving up seven inches. Dale Solomon, Tech's leading scorer, suffered almost as much. With Sampson negating his favorite around-the-basket shots, Solomon had to be content with garbage points and occasional jumpers. The result: four of 14 shooting and 16 points. But he didn't have a point in the second half until the game was well out of hand.

After their victory over North Carolina Wednesday night, the Cavaliers admittedly had trouble getting properly psyched for this one. Perhaps that explains the lackluster first-half performance that had Coach Terry Holland burying his hands in his head frequently.

Holland saw much more of the second half. After their 12th turnover, the Cavaliers looked like the nation's third best team. A 20-footer by Tim Mullen, a 12-footer by Othell Wilson, a 16-foot shot by Jeff Jones and another jumper by Wilson from midrange jumper had Moir wondering what to do next. He never came up with an answer, and Virginia gradually increased the lead to 26 before Holland turned things over to his second-stringers.