A baseball player's batting stance is his consciously created statue of himself--a self-portrait. It has always been Carl Yastrzemski's personal, and curious, virtue that he has been willing to change his stance, radically and often.

The alterations have come not merely in his stance at the plate--although, among stars, he has been singularly willing to tinker with success. Yaz also has changed his mental and emotional stance--his whole posture toward the game and the baseball world.

In short, Yastrzemski grows.

This familiar fellow, who will be 43 in August, once again looks dramatically different, at the plate and away from it.

At bat, he is a revitalized .330 hitter, leading his first-place Boston Red Sox in runs batted in (21).

"I found my new stance with three days left in spring training," he said. "I'm quicker, have more power. I'm really swinging hard again." After four aging seasons of mild statistical embarrassment, like last year's .246 average, Yastrzemski seems intent on a career finish worthy of the start.

Away from the box, Yastrzemski, whose strained face has long seemed perfectly attuned to Boston's tradition of disappointment, is equally changed.

A shy smile has replaced the great hitter's characteristic look of pained, slightly annoyed concentration. Now, Yastrzemski goes out of his way to laugh, although this novel expression seems to contradict all the down-turning character lines of his face.

"At times, I thought it was talent alone that won, but, now, I think you need togetherness, too," said Yastrzemski, who has, with the years, gone from superstar recluse to stoic veteran leader to a cheerful old goat who's just doin' the best he can. "Being on this team is the most fun I've ever had."

Through 22 seasons, Yastrzemski has been a coil of implacable intensity. Although only 5 feet 11 and 180 lean pounds, he has hit 431 home runs and swung hard enough to propel balls 500 feet. His seizure of a swing seems like a paroxysm intended to dislocate a shoulder or wrench a knee with its corkscrew violence. Yastrzemski seems to hate the ball, wish it personal harm, as though pent-up hostility were fueling him.

Yet, although the force was constant, the form varied. His stance has been so closed that he resembled Stan Musial. He has held his hands as high as if a thug had just poked a gun in his ribs. He has waggled and he has been frozen. And, in recent years, he has resembled a man leaning forward to peek around a corner while simultaneously hailing a taxi by waving an umbrella.

As he has changed his hitting tendencies, changed the "book" on himself, Yastrzemski has been almost everything except "normal."

"I've tried so many different things, there wouldn't be enough pages in a book for 'em," said Yastrzemski, who has been an opposite-field hitter (early years), an all-fields power hitter (midcareer), then a "dead pull" hitter. Along the way, he has changed from a fast-ball hitter to a breaking-ball killer, then back.

Now, Yastrzemski looks almost conventional.

"I kept telling him," said Walt Hriniak, the Red Sox batting coach, "that every good hitter, somewhere in his swing, reaches a point where his hands are ear-high and cocked at about a 45-degree angle. So, why not start it there? Very logical. Common sense."

Gone is that awkward, off-balance crouch. "It was tough standing that way," Yaztrzemski said, "let alone swinging . . . but, before I hurt my Achilles (in 1979), I was tearin' it up with that stance."

Only with Yastrzemski would such "logic and common sense" seem out of place. His baseball signature has always been a defiant Dali scrawl--utterly different. Now, the time has passed for being solitary. He is more than glad to heed a coach's nagging, to trade glory for fellow feeling.

The Yastrzemski face, which seemed made with heroic melancholy in mind, now seems relieved that the days of superstardom, of chasing 3,000 hits and 400 homers, are over. No more megarecords are within his reach. The Red Sox themselves, stripped of big names, are no longer burdened with too-great expectations. Yastrzemski can relax, a little, at last.

On the bench, he blends easily, talking about how "Burgy (reliever Tom Burgmeier) and I caught a half-dozen walleyes today." Instead of being the man perceived as looking over the manager's shoulder, Yastrzemski and skipper Ralph Houk are buddies. If Yastrzemski had a spare life to live, it wouldn't be hard to imagine him using it to duplicate Houk's rise from private to major as an armored division Ranger who got the Silver Star, Purple Heart and Bronze Star; a hero at Bastogne, in the Battle of the Bulge.

Houk said recently, "I'm lucky that my veterans, like Yaz, are hard workers by nature. That rubs off . . . Statistics don't mean anything. It's the things you do that win that count, like all the runs Yaz drives in from second base with two out . . . I came to the ballpark late today so that damn (injured) Yastrzemski couldn't talk me into putting him in the lineup."

All the weight isn't on Yaztrzemski. When he has an injury, like his current pulled groin muscle, he can take three games off to heal and nobody makes it a federal case. "I've learned that I need some time off now to give the muscles a chance to rebound," said the longtime Mr. Play With Pain.

Finally, baseball has become simple and pleasant--one game at a time for the sake of the game itself, and for the bushy-tailed young team that reveres him. "I don't look back one day or ahead one day," said Yastrzemski. "I forget yesterday. Only today matters. Helping the club today.

"This team is a good mixture, a very close club that pulls for each other . . . a hell of a unit. Just watch the reactions on our bench. If you're a little down, all of a sudden guys are patting you on the back, shaking your hands, getting you psyched up."

Why is Carl Yastrzemski--second in history in games played, fourth in bases on balls, seventh in total bases, 10th in hits, 11th in extra-base hits, 12th in RBI--still aggravating himself with groin pulls and the search for new stances?

"Want to get it all one time," he says, meaning the world title no Boston Red Sox team has won since 1918. "Don't know whether we will or not, but we'll be in there fighting."

This time, together, with no I's, just we's.