Spring training is for rookies. This month, we try to tell trash from treasure.

As each young busher steps to the plate or mound, we watch him with an attention he may never command again. Here, our powers of discrimination are truly strained. What fan can resist watching these exhibitions and, without the crutch of big league statistics, try to predict a player's future.

No matter what a man's minor league record, we know it doesn't necessarily translate into big league performance.

We take a few glimpses of a player--his movement as he skims toward the ball, the speed of his wrists as he tries to get the bat head out to pull an inside fast ball, the tightness of spin and tilt of his breaking ball. Then, from these scraps of data, we imagine we can conceive his entire career. It's an addictive pastime.

Recently, the Orioles have been fascinating to watch because they've been correct so often in evaluating players. With exceptions like Bob Bonner and Dave Ford, the team has usually spotted its Murrays and Ripkens, Flanagans and Davises, ahead of time and predicted their levels of future performance.

This spring, the Orioles chant three names: John (T-Bone) Shelby, Leo Hernandez and (Mighty) Mike Young. Not since 1977, when nine rookies made the team, have the Orioles been so high on so many prospects at one time.

"Shelby, Young and Hernandez are all going to be better-than-good major league players," said Manager Joe Altobelli.

In 1982, Baltimore had three clear weaknesses--center field, third base and right field. Shelby plays center, Hernandez third and Young right. Whether preparation or providence, no one knows, but the Orioles aren't complaining. To heighten piquancy, all three are difficult prospects to judge. Taken on past numbers, plus their visible skills and weaknesses, each could be star or flop.

Shelby, a gifted fielder, is a switch-hitter with a tad of power and some base-stealing speed. However, Shelby was, until '82, a weak left-handed hitter; his theft percentage is only fair and his 17 homers last season even surprised him. A .250 career minor league hitter, Shelby, 25, will probably never have seasons to match Al Bumbry's productions in '79 and '80.

"Shelby fits so well," said Altobelli. "He can play every day. Or he can pinch-run, pinch-hit, play defense, start against some left-handers who are tough for Bumbry, depending on what you need. He makes a good problem in center field. He seems to be a polished player now."

"Shelby has nothing but stardom ahead," said veteran John Lowenstein. "He's a natural. There's room for him and he's gonna have to play."

Even Bumbry, whose job is in jeopardy, said, "It's inevitable that Shelby makes the team. He's ready, so he might as well help the club."

"I'm sure that everybody is saying that I can't come back," added Bumbry, "but if my legs are healthy again, I can still do the job. When my legs got better (in September), I finished '82 with an 11-game hitting streak.

"Everybody wants this to be 'Who's going to win the job ?' " said Bumbry. "It doesn't have to be one way or the other. We can both contribute."

"Bumbry has helped me out more than anybody, said Shelby. "I can talk to him. I won't wish any bad luck on him. I think it helped both of us when I came up last year."

Hernandez has the build and power of a Sal Bando. He's had five excellent minor league seasons, with a .295 average, plus 25 homers and 110 RBI every 600 at bats. He has a nice, swaggering macho presence about him and even stole 20 bases last year. Buried in the superb Dodgers chain, where he never got a chance, he could be the sleeper of the season.

"He's an animal," said Frank Verdi, Orioles' minor league manager. "I mean that as a high compliment. He attacks everything."

On the other hand, when the savvy Dodgers cut you adrift, especially for 38-year-old Jose Morales, there's usually a reason. Told of the high grades Hernandez was getting, Dodger Ron Roenicke said, "He must have improved . . . Leo had a lot of holes (in his swing) and he wasn't much of a fielder."

"Everything about Hernandez has been 50 percent better than I expected--his poise, his arm, his defense, his fundamentals and alertness, his actions at the plate," said Coach Ray Miller. "He's laid off some pitches that we were led to believe he'd chase, and he's hit some good pitchers' pitches. When the Dodgers let somebody go, you're always waiting for the other shoe to drop. But Leo's been a little bit awesome so far. Maybe we stole one."

When Hernandez, a Venezuelan, had visa problems and reported on time but later than any other player, the team's brass was braced for trouble. Had they traded for a bad attitude?

Instead, the Orioles have discovered a quick-study hard worker who says all the right things, seems confident and speaks perfectly serviceable English.

"I'm ready. I had a good year every year for the Dodgers but I never got a chance. I think I'm ready to play. My mind is on the major leagues," said Hernandez. "I'm happy. This is like a new life, a new career . . . No problem."

"Hernandez is going to play a lot this spring," said Altobelli, "because in order to make a decision we need to see him."

While Shelby and Hernandez might both be in the starting lineup opening day, the switch-hitting Young is for the future. He's the definition of raw diamond--all power and speed and enthusiasm, but handcuffed at the plate by heat inside. One more AAA season should pin down whether he's star prospect or another free-swinging suspect.

"We think Mike Young is going to be another Eddie Murray with the bat," said Altobelli. "You figure maybe he should start in AAA, set the league on fire, then come back and do the damage he's supposed to do."

In baseball, unlike much of the rest of life, all our questions are eventually answered. How nice that time will tell.