Before he's through, Vince Coleman might make baseball alter, or even abolish, the balk rule.

Few players are so good that the rules or dimensions of their games have to be changed to contain them. But it happens. Basketball widened its foul lane. Pro football moved its goal posts.

Someday, with Coleman as catalyst, baseball might have to decide if pitchers ought not be allowed to "cheat" to keep runners from larceny.

After all, should one player really steal 200 bases in a season?

You can snicker, but don't laugh.

This St. Louis Cardinals rookie, who already has stolen 78 bases in 96 games in the majors, might someday set such a preposterous record.

It took another Cardinals left fielder -- Lou Brock -- a career to set the National League mark of 118 steals in a season. At his current pace, Coleman would break that mark with 122.

Sunday, St. Louis pitcher Danny Cox asked Coleman how many bases he thought he could steal if he ever learned how to draw 100 walks a year and bat way above .300, like Rickey Henderson of the New York Yankees.

Coleman, who's hitting .270 and will draw about 50 walks this year, said calmly, "Maybe 300 bases."

He presumably was joking. But how much? Why not 200 steals?

Two years ago in the minors, when Coleman batted .350 and had a .425 on-base percentage, he stole 145 bases. In 113 games.

Drum roll. Rim shot. Double take.

Can Henderson's major league record of 130 steals be far away?

"Anything is possible," says Coleman, words few athletes would ever dream of saying. "You never know what you can do."

You never know what Coleman can do.

Even since Maury Wills broke the 100-base barrier in steals with 104 in 1962, baseball has wondered what would happen if the game produced a base runner who had world-class speed, great acceleration, an alert attitude, good work habits, serious ambition, utter reckless confidence and toughness.

First Brock, then Henderson and Tim Raines -- all 100-plus men -- came closer to the abstract ideal. But none of them had it all.

Now comes Coleman.

At 23, he runs the 100-yard dash in 9.4 and the 40 in 4.3. His quick start is even better than his raw speed. At 6 feet, 170 pounds, all muscle, this former football player at Florida A&M is a dangerous projectile when he slides spikes first and hard; nobody enjoys tagging him. Coleman also is bright and studious.

"Great attitude. Great work habits . . . Serious on the field and fun off it," says Manager Whitey Herzog.

Even his stats say nothing of Coleman's potential. He learned to switch-hit only in 1982. His .270 average figures to improve. Maybe a lot. Phillies catcher Ozzie Virgil says, "The only place to stop him is at the plate."

"Once he gets on base, maybe we should just deliberately balk him to second and third, then concentrate on the hitter," says the Phillies' Mike Schmidt. "Right now, he's just playing havoc with everybody's mind."

"Last time we played them," says Phillies Manager John Felske, "their pitcher was on first base and Coleman hit a grounder to shortstop. We got the forceout. Then the coaches and I looked at each other and said, 'Did we do that wrong?' Maybe next time we should throw Coleman out at first and let the pitcher go to second."

That shows how radically Coleman has shrunk the diamond and changed base-running conventions. He served notice the way he usually does -- fast.

In a 10:30 a.m. spring training exhibition B game, he scored from first base on a routine hit-and-run single to right field. When the ground ball eluded the second baseman's lunge and died quickly in the dewy grass, Coleman never stopped churning.

"Ah, it wasn't that big a deal," needles Cox, "the right fielder had no hose (arm)."

Last week, Coleman even shocked himself. And that's hard to do because he's planned on being a pro athlete in some sport since he was a boy growing up in Scott Park in Jacksonville watching stars like Harold Carmichael, Truck Robinson and Terry LeCount.

Against the Cubs, Coleman became the first man to steal two bases on one pitch. Sure, he had stolen second and third base in the same inning seven times. And he'd appropriated more than one base in a game 22 times. And he'd even stolen home once.

But how do you steal two at once?

By mistake, of course. You overslide third base, touching it on the way past. Then, with the gall known only to great talent, you head for home plate instead of meekly diving back to third and a certain out.

In the subsequent rundown, the Cubs got so flustered that nobody covered the plate and Coleman trotted home standing up. Willie McGee, who had been at first base, also got credit for two steals on the play, though he merely was slipstreaming in Coleman's surrealistic wake.

"He's intimidated a lot of people this year," says Herzog, who gladly traded grumbling, erratic Lonnie Smith to Kansas City in midseason to give Coleman sole rights to left.

On the bases, Coleman looks at hardship as challenge. When one Montreal pitcher, after a first-pitch-of-the-game single by Coleman, threw to first base 13 straight times, Coleman promptly stole second and took third on a wild throw on the first pitch to the plate.

"He's completely aggressive and confident," says Cardinals veteran Ozzie Smith.

Lots of that came from the pro tradition of Scott Park, then Florida A&M. "I always wanted to be a pro athlete," says Coleman, who was invited to try out with the Washington Redskins as a punter, but lost interest when he was asked to return punts.

Of the celebrity side of his job, he says, "I enjoy it. I was trained for it (with college courses in speaking). I prepared myself for it."

To be a star?

"I'm not a star. I'm just an average player."

In a limited sense, that's almost true. Although he is a good outfielder, there's a limit to how much greatness can be claimed for a .270-hitting rookie with only one home run (inside the park) and only 23 RBI in 406 at bats. Of his hits, 26 percent never left the infield.

Coleman will chase bad pitches and strikes out almost as often as he steals. Like many a speedster, first base is his toughest theft. If he improves at the plate, his nickname will be "Havoc." But, if he ever loses confidence at the plate, "average ballplayer" still could be his fate.

On Saturday, Herzog held Coleman out of the lineup against 42-year-old Jerry Koosman, who'd bamboozled the kid in 11 straight at bats this year. "Koos has had him chasing pitches in the dirt, over his head," said Herzog.

Before that game, Coleman, out of the lineup, walked alone up the dugout tunnel. Until Herzog caught up, threw an arm around him and wrestled him to the clubhouse like a bearish brother.

Vince Coleman still needs a little protection. But probably not for long.