If there ever has been a football coach unflappable in victory and defeat it is Maryland's Jerry Claiborne. His emotions, whether they be joy or sorrow, rarely show.

But yesterday, after watching his team play its heart out and lose to Penn State, 24-10, on an overcast afternoon in Byrd Stadium, Claiborne was shaken.

It didn't show as he shook hands with Penn State Coach Joe Paterno, his record now 0-8 against Paterno, who at 53 is one year Claiborne's senior. hIt didn't show as he trudged through the crowd to the locker room.

But it did show when he talked about the game. He had completely blocked the game's key play from his memory.

"I thought the big thing for them when we were ahead, 10-3, was the punt return," Calaiborne said. "That set them up in our territory and they went from there. The tying touchdown was just real great catch, a perfect play."

But the punt return and the touchdown catch Claiborne referred to had come with the score tied, 10-10, someone reminded Claiborne.

The coach, who can usually recite every play in a football game from memory without pausing for breath, did a double take. "You're right," he said, the unpleasant memory suddenly returning. "That drive (80 yards, six plays) was their best of the day. I remember telling our defense what an important series it was before it went out there."

For Claiborne, this loss was harder to take than the convincing losses the last two weeks to North Carolina and Pittsburgh.

Even 15 minutes after game's end, he was still feeling emotional. His voice was soft, his answers to questions calm, not combative as they often are in defeat. He even referred to his players as "kids," in talking about how hard they had fought. Normally they are "players," or "men." Yesterday, to their coach they were a group of kids who had given him 100 percent after he had put them through their toughest week of practice all season.

Watching them leave the field, bruised and battered and with no victory to show for their efforts, clearly moved Claiborne. For the Maryland players, getting him to show that kind of emotion was almost as big a victory as beating Penn State would have been.

The Terps played without defensive back Sammy Johnson, whose sprained ankle wasn't ready . . . Several new injuries: fullback Jeff Rodenberger again pinched a nerve in his neck, the second time this season . . . Linebacke John Kreider bruised a shoulder injury.

Paterno went out of his way to compliment Mike Tice, who, in spite of three intercepytions, played superbly for three quarters . . . Maryland and Penn State do not play next year or in 1983. They will play at Penn State in 1982 and 1984, so the Lions won't be here for at least another five years.