IT WAS A GLORIOUS SPRING-TRAINING day at Phoenix Municipal Stadium, and all the savvy regulars were gathered in the press box to take in the action between the Oakland A's and the Chicago Cubs. But who was that stranger among them—that burly, bearded fellow with the manner of a gentle grizzly? One of the old baseball hands in the booth, Dave Garcia, a former major-league manager now scouting for the Milwaukee Brewers, eased into the chair next to him. Garcia struck up a conversation, which somehow wandered onto the arcane topic of great minor leaguers who never made it in the majors.

Garcia mentioned Jesse Levan—a name that probably few in the press box had heard. "Hell of a hitter," said the stranger. "He played in the majors, you know. About 20 games. Hit a grand-slam homer." Impressed, Garcia asked the stranger's name. "I'm Bill James," the big man replied. Garcia's face lit up. "Ah," he said. "The stats man!"

The baseball world has always loved statistics, but no one has ever found such depths of meaning, such hidden passions and, yes, such poetry in them as Bill James. In 1977 the ex-high school teacher from Lawrence, Kans., began publishing his annual Baseball Abstract, a volume that became as much a part of each season as the crack of the bat and the green fields of opening day. In it, James would plow through stacks of statistics and put them to work: evaluating players, scrutinizing strategy, challenging conventional wisdom. The Abstract became sacred text for the faithful, an invaluable handbook for insiders and a godsend for the armchair fan—proof that you didn't have to be able to spear a grounder or hit a curveball to outfox the pros.

James, 41, has revolutionized the way people look at the national game. In the epoch B.J. (Before James), hitters were judged by simple measures like batting averages and home-run totals. Not good enough, said James. Instead he invented a statistic called "runs created," which factored in things like walks and extra-base hits. By that measure, he showed that players like Gene Tenace of the Oakland A's and Dwight Evans of the Boston Red Sox were underappreciated stars.

Fielding statistics were another James bugaboo. Players who commit the fewest errors, he argued, are not necessarily the best fielders; the key question is how many balls they get to. Fans of Bobby Murcer, long praised for his defense, were not happy: In 1975, according to James's criterion, Murcer—then with the Chicago Cubs—had been the lowest-rated right fielder in the major leagues.

With contrariant opinions like these, James staked a claim to his favorite position on the diamond: designated outsider. His mix of midwestern modesty and good-humored bullheadedness seemed just right for the job. "As I saw it," he says, "baseball had these mountains of numbers: the box scores. And it had these mountains of things that people said all the time: 'Baseball is 90 percent pitching,' or 'You can't win without a strong bullpen.' I just made the effort to see if the data bank supported the things people said."

Very often, he found, it didn't. When pundits claimed that a player's prime is between the ages of 28 and 32, James did his own study and found that most players actually peak at age 27. When someone claimed that Reggie Jackson did best in front of big crowds, James crunched the numbers and found out that Reggie actually hit best in front of crowds of 10,000 to 20,000.

James's methods have had a mighty impact. Sportswriters and TV broadcasters now routinely cite the statistics that he popularized, like how a batter hits against right-handed vs. left-handed pitching, or with runners on base. Newspapers like USA Today and the National are filled with Jamesian stats. James is also the patron saint of so-called rotisserie leagues, in which fans pick their own fantasy teams and compete via statistics, a pastime that now claims an estimated 1 million enthusiasts. (His methods touch his personal life too. When James realized that his chances of picking a matched pair of socks out of the drawer were less than 1 in 20, he switched to all brown socks.)

No player, owner or agent can afford to ignore James's data, especially at contract renewal time. James, in fact, works as a consultant for agents Alan and Randy Hendricks (who represent Boston pitching star Roger Clemens, Cy Young Award winner Doug Drabek of the Pirates, and others), providing statistical workups on players who are preparing to go into salary arbitration.

"One of the problems in baseball is being able to judge a guy's value to the team," says Joe Morgan, the Hall of Fame infielder now broadcasting for ESPN. "A 260 hitter can be more valuable than a 300 hitter. A player who hits 35 home runs may not drive in 100 runs. All those things were brought into focus by Bill James."

Yet in 1988, lamenting that baseball's stat explosion had grown into "an eyesore," James announced he was abandoning his annual Abstract and dropping the purely statistical approach. "I was never a good statistician," he says. "I'm sloppy. I'm impatient. What I was good at was tying the numbers to the discussion." He took a year off, then returned with a new, more impressionistic annual look at the game, The Bill James Baseball Book. It contains player analyses, historical essays, predictions and articles on anything that strikes James's fancy.

A glance at this year's edition. published in March by Villard Books, reveals that, with or without stats, James's opinions are as contentious, idiosyncratic and wide-ranging as ever. An analysis of Milwaukee infielder Gary Sheffield becomes a critique of psychology—a discipline whose "grand promises," James says, have gone unfulfilled. In one chapter James dissects the factual inaccuracies in David Halberstam's much-praised baseball book The Summer of '49 (example: Jackie Robinson did not steal "at will" on Yogi Berra in the 1947 World Series; he stole only one base).

James works out of a shabby three-room office on the town square in Oskaloosa, Kans., an hour's drive west of Kansas City. The furnishings include racks of baseball reference books (among them, seven biographies of Joe DiMaggio) and a battered couch on which James parks his 6'4", 250-lb. frame when deadlines require an all-nighter.

He attends 35 to 40 games a year, most of them at Royals Stadium in Kansas City. (James's estimate of the time it takes to walk from his parking spot to a seat in the stadium: four times the square root of the game's attendance.) Once in a while he will get press credentials and visit the locker room after the game, but he rarely talks to players and shies away from sportswriters. "As a group, they are very cynical," he says. "Their humor seems to consist almost entirely in putting each other down and putting the players down."

Trips to the ball game often turn into outings for wife Susie and the two James children, Rachel, 5, and Isaac, 2. "I'm a pretty good fan now," says Susie, a painter of landscapes and interiors who has done the cover illustrations for some of James's books. She listens to Royals games while working in her upstairs studio in their 14-room, antique-filled Victorian home. Not that baseball is the James family's whole life. Bill and Susie take time out for frequent "date nights" at the movies (a recent favorite: Mr. and Mrs. Bridge), and this spring they took the kids to Arizona for some visits to the zoo and—well, yes, a few Cactus League ball parks. (Bill's estimated winning percentage in arguments with Susie: 228.)

The youngest of six children, James grew up in the tiny northeast Kansas town of Mayetta. His father sold cream to local farmers; his mother died when he was 5. As a kid he played a little baseball but wasn't much of an athlete. ("Volleyball was the only sport I was any good at," he says.) But from the age of 11, he listened religiously to Royals games on the radio. His knack for numbers showed itself early. By the time he got to the University of Kansas in Lawrence, where he majored in English and economics, he could amaze friends by instantly multiplying any two numbers they shouted out.

After a stint in the Army and two years as a special education teacher, James quit to try writing about baseball. To make ends meet, lie took a job as nighttime boiler attendant at a Stokely—Van Camp pork-and-beans plant in Lawrence. (William Faulkner, James likes to point out, was a boiler attendant while revising The Sound and the Fury.)

While contributing articles to various baseball magazines, James began working on what he and Susie (a secretary at Stokely, whom he married in 1978) dubbed his "secret project." His first Baseball Abstract was a typed, 68-page manuscript, stapled together and mailed to people who ordered it through ads he placed in the Sporting News and other baseball publications. James did all the figuring himself, without so much as a pocket calculator. He culled the numbers from daily box scores and wrote each major-league club individually for stats. (At peak writing speed, James chugs 2.5 diet colas per page.)

It wasn't long before the Abstract began to gather an underground reputation. One year Norman Mailer sent in $5 for a copy. James was so flattered that he returned the check. Mailer sent the money back with a note: "If ever an author earned his $5, you have." After five years of printing his books privately, James signed with Ballantine Books in 1982, and his fortunes began to soar.

Today, James's enterprises include a part ownership of Stats, Inc., a St. Louis—based company that produces an annual book of baseball statistics and runs a more complex version of rotisserie baseball called the Bill James Fantasy League. (James himself had two fantasy-league teams last season; both had losing records.) He also appears on a weekly syndicated radio show, Baseball Sunday.

Though he is passionate about baseball history, James is not one of those traditionalists who rail at changes in the game. He has no nostalgic affection for daytime baseball. "Baseball was made to be played at night," he says. "You're more focused on the game." Soaring player salaries do not trouble him: "Baseball is a business that generates huge amounts of money. I've never been able to understand the social good in [owners] Gussie Busch or Ewing Kauffman or Peter O'Malley keeping the money for themselves."

James is occasionally tempted to apply his statistical approach to other sports. In basketball, for example, he is tired of hearing announcers claim that most games are won in the fourth quarter. "I'd like to study whether that's true. How often does a team ahead after three quarters go on to win?" Many people have suggested that he apply his methods to another potentially lucrative subject: the stock market. James says the prospect leaves him baffled. "I can't get past step one," he admits.

Besides, there's something special about those baseball statistics. "The numbers associated with baseball are peculiar in that they exist as extensions of a network of standards," says James. "They are not just numbers; they convey human images. For example, 38 home runs conveys an image of power; 65 stolen bases conveys an image of speed."

And 300-plus fiercely argued pages each year, about a game in which 26 teams play 2,100 games to determine one world champion, convey the image of a guy having the time of his life.