So it was absolutely certain where Carl Yastrzemski could be found more than two hours before the game Friday night, at work in the batting cage, alone in Fenway Park save for two coaches -- one pitching to him, the other watching his every movement -- and as many pigeons as fans. Yaz wore a batting glove and a worried look.

"Try to get comfortable," the hitting coach, Walt Hriniak, would say, softly but more and more as an order. "Try to get comfortable. Try to get comfortable."

Try? Of course, Yaz would try. He has been trying, busting his butt like few players -- and fewer superstars -- ever in baseball. If even casual fans would not be surprised that a 42-year-old with such a dip in his baseball life signs would work overtime, the Fenway Faithful know even if he was hitting .330 with an RBI a game, he might opt for extra practice.

Nobody uses the batting cage as a lab quite like Yaz; nobody experiments more with what has made him extraordinarily successful; nobody is more willing to retool his entire stance, seemingly on whim at times, so that he looks like Stan Musial one at-bat and George Brett the next; nobody needs to tinker more, he suggests.

For 45 minutes of near-solitary confinement, Yaz has belted baseballs from almost every reasonable part of the batter's box, from the front and back, sometimes with both feet planted and sometimes with his front foot on tippy-toe, sometimes with the bat high and straight and sometimes with it at a 45-degree angle. Suddenly, the dark mask on his face is gone and a smile appears. He talks rapidly with Hriniak, points toward the batting-practice pitcher and says:

"He's not telling me what's coming, either."

Even in his most glorious year, 1967, when he led the American League in hitting (.326), runs (112), hits (189), RBI (121) and tied for the lead in homers (44), Yaz made significant adjustments with his stance. With most players, a stance is as unique -- and permanent -- as his fingerprint. Yaz switches stances as often as some Central American countries switch governments.

At age 22, his first in the majors, Yaz hit .266 in 148 games and drove in 80 runs; At age 40, in 1979, Yaz hit .270 in 147 games and drove in 87 runs. In between, he did a whole lot more.

"My rookie year," he said, "I had a stance they compared to Stan Musial's. I was that closed, in a crouch, and I moved the ball like that." Three months later, Stan would say the stance looked most unusual.

"When I struggled over that period, after hitting nearly .380 in the minors one year and nearly .340 the next," he said, "I ditched that, went to a straight-up-and-down stance. The reason I changed was I got jammed a lot when I first came up, by the slider. Guys like (Frank) Lary and (Jim) Bunning jammed the hell out of me.

"I went from about .210 to (about) .270, hit .340 or .350 the second half of the season."

The what in his stance is mysterious; why he changes is not.

"I've always gone on the theory: 'hit the fast ball and adjust to everything else.' So the main thing, when I make a dramatic change, is to make sure I still hit the fast ball. One thing I haven't lost is the quickness of my hands, so I want to make sure I don't change to anything that'll block my hands out."

That is why Yaz grabbed Coach Tommy Harper, after that preliminary work with Hriniak, and spent another half hour in a closed cage beyond the center field wall. Though a right-hander, Mike Norris, was pitching against the Red Sox, Yaz was not a starter. So after hitting with the other extras, while the regulars were honing their swings in BP, Yaz and Harper went off in search of yet another stance.

To assure that Yaz would not invent any useless hitches in his swing, Harper stood about 30 feet away, or not quite halfway back to the mound, and threw as hard as his arm would allow. (He is more than a year younger than Yaz.)

"When you think about Yaz," Harper said later, "he almost had to make an adjustment, 'cause his style was so unusual in that when he was younger he held his bat way up above his head. The older you get the less movement you want to make. He just couldn't get around. So over the years he's come down. In '67 he was holding it way up. I played with him in '72, '73 and '74 and he started gradually coming down with it."

How dramatic have his changes been?

"Unbelievable," said Hriniak. "He's gone from a vertical bat to a 45-degree-angle bat, from a straight-up-and-down stance to an extremely crouched, front-shoulder-down stance to a more modified, realistic stance right now."

Right now, less than an hour before Friday's game with the A's, "he's a little frustrated, trying to find something that's workable," Hriniak said.

There is another adjustment.

"A transition for him," Harper said, "from regular player to in and out of the lineup. Some players get used to it quickly and early, because they're not great. But you take an every-day player and make him part-time, especially after 20 years, and it's quite an adjustment."

Immediately before the game, Yaz, with streaks of gray in his hair but an almost child-like desperation to learn, stalked Hriniak for more advice about batting chemistry, how much drop in stance will add more pop to the ball, make it dance.

Almost everybody in Fenway popped the ball against Norris and the A's relievers, to the point where Yaz got to play first midway though the game. In two at-bats this night, we saw the quintessential Yaz, the thinking Yaz, very likely the insecure Yaz, an amazingly durable man not totally cocksure about his ability.

Twice he faced lefty Bob Owchinko, who brought a 1.76 earned-run average from the bullpen in the fifth. Playing Musial, or a reasonable likeness, Yaz looked horrid, swinging badly at a bad pitch for strike three. Yaz may be fooled twice in a row, but he is obsessed with not looking foolish the same way.

Next time up, there seemed an entirely different player inside that uniform. Instead of leaning toward the pitcher, Yaz had a good deal of weight on his back foot. He stroked an RBI single to right, and later laughed about it.

"I'm just a firm believer in changes," he said. "I'm not a big guy. I can't be fooled, lose a hip or a hand and still do something with the baseball. Everything's got to be perfect. I guess that's why I've changed so many times over the years.

"The past few years I've leaned toward the pitcher, to the point where I was almost falling over. That was to keep my front shoulder down and use my hands more. This year, I've straightened completely up, the Charlie Lau theory. I've always been an aggressive, attack-type hitter my whole career, and that stance doesn't agree with Lau's theory. So it takes awhile to adjust.

"First time up, I defeated my whole purpose. I was getting out even harder on the ball than before. Second time was Lau's theory, which Hriniak teaches, which is getting your weight back, very soft and smooth gliding into the ball. It's completely opposite to the way I hit my whole career."

Yaz offered another rare smile.

"What am I going to use tomorrow?" he said. "I don't know yet."