If baseball is just a kid's game, why do the children who play it seem so old?

Look hard at Scott McGregor, 24, for traces of youth. Those are gray hairs among the brown, put there by hanging curves.

McGregor's voice is soft, his manners perfect. His Oriole mates joke that they have never heard him swear.

That did not keep the gentle southpaw's eyes from looking as scalded and burned out as a shellshocked war veteran after he was bombed by the New York Yankees a fortnight ago.

Of all the frightening passages in a career, the most harrowing is the first crisis of confidence in the big leagues. That's where McGregor lives now, at the corner of Self Doubt and Insomnia. It's a tough block.

"I keep telling myself everything's going to be all right," says the 1-3 Oriole with the albatross ERA - 11.15. "I can't be this bad."

Usually, pitchers stand on a hill. By last weekend in Chicago, McGregor had fallen into a black hole. In a dozen innings, he had given up a score of runs. Even McGregor's phone number had been changed. You had to dial "75" - the bullpen - to reach him.

McGregor and fellow lefty Mike Flanagan, 26, talked deep into the a.m. in a Chicago hotel, digging into the crevices of the mind.

A pitcher's psyche is the most unstable element known to baseball, the uranium 235 of the sport.

"Your self-assurance can range from a complete game all the way down to a single pitch," Flanagan had told McGregor. "I went through it all last year.

"Sometimes you are so sure of yourself that you can arrange the whole game in your mind nine innings at a time . . . pitches to emphasize in parts of the game . . . how to set up hitters in different at-bats.

"Other times, you just say, 'Let me get through the middle innings and I'll worry about the eighth and ninth' or 'Gotta bear down early and not get knocked out.'

"And sometimes you're struggling so bad that you can only worry about one inning, or one hitter, at a time."

McGregor, unfortunately, had sunk lower. His delivery was messed up; he wasn't changing speeds enought; his control was shot, and as soon as the bases became crowded, every hitter looked like he should have a candy bar named after him.

"Scott," said Flanagan, "was down to dealing with the game one pitch at a time. I've been there It's scary."

With McGregor summoned to that blustery, raw Chicago mound, the Oriole bullpen was empty. McGregor was the last available man.

The first White Sox singled to tie the score, the second walked to fill the bases, the third got ahead on the count.

Manager Earl Weaver came to the mound to visit one of the supposed mainstays of his staff, a mainstay about to fly apart.

"Earl just said, 'I can't come out here again and I ain't got anybody left in the pen,'" said McGregor.

Weaver, down to last resorts, was telling McGregor, "It's sink-or-swim time, kid. This merry-go-round is all yours."

McGregor snapped off a beaut of a curveball and escaped the seventh.

"That one pitch shook him out of it," said pitching coach Ray Miller. "He got the last seven outs in a row and threw some hellacious curves in tough spots. Scotty getting a win was the only good thing that could have come out of that miserable game.

"Talk about super happy . . . you shoulda seen those 24 other guys when Scotty came off the mound."

McGregor now has one eye peeping over the top of that black hole. The rest of him is still deep in it. Like some other Orioles, McGregor simply has not proved that he can be a front-line major leaguer.

The Baby Birds are earnest infants, their clubhouse characterized by a charged silence. Larry (Hawk) Harlow won't explain how, in one year, he has transformed himself from a career .260-hitting AAA player, into a guy with a .375 average. Hawks hate jinxes and don't tell their secrets.

Hyper-intense Rich Dauer, a genuine phenom at every level, except the majors, walks around the locker room like a condemned man. Last spring, he went 0-for-April and 1-for-May. This year he's improved: he was 2-for-April. The Orioles are beginning to wonder.

McGregor is far from alone. The young Orioles are a team under the gun. Can Easy Billy Smith hit a lick? Is 6-foot-7 Tim (Big Foot) Stoddard terminally wild? Can Kiko Garcia field enough to play shortstop or hit enough to play anywhere?

The question aimed at McGregor are the only ones of Magnum Force. The Kikos and Hawks and Big Foots can come along more slowly. McGregor is being given his Big Chance now. His career record says that if he hasn't been prefectly prepped for the assignment, no one ever was.

Since the Yanks drafted him No. 1 and compared him to Whitey Ford in 1972, McGregor has been a steady climber, bearing the tag, "Good for sure. Maybe near-great."

Now, the doubts are rising. McGregor may have blistered the International League in '76 and given Puerto Rico a 2.22-ERA hotfoot in the last off-season, but in his second full Baltimore season, he has only four career victories.

"Everybody is crazy about the kid," says former Brooklyn no-hit pitcher Rex Barney, the O's PA announcer. "Perfect attitude . . . with all the pompous meatheads in the game, he's the kind you root for. But you ask if he isn't a little short on raw stuff. Is he mean enough? Does he need another pitch?"

Down in his dark hole, McGregor can hear the gossip.

"You keep getting knocked around, but you can't panic," says McGregor. "I've seen guys think themselves into slumps so deep that they never got back out." You practically have to relearn yourself. Loss of faith in your self is the only thing that can really undo you."

McGregor has lost the vital faith before. "In '75 at Syracuse my record was 6-9. When I broke my collarbone, I said, 'That's typical of this rotten season.' I thought every hitter was tougher than he was," McGregor said. "I had lost confidence. Then it all clicked one night and I had the chemistry back. I can't explain it.

"They can tell you how to pitch 8 million times, but experience is the only teacher. Baseball sense gets knocked into your head one line drive at a time."