Theo's Red Sox career: Brief. Brilliant. Gone.

Theo Epstein lived his dream at something like warp speed. After growing up in the shadow of the Red Sox's Fenway Park, he took over, at 28, the storied franchise he'd cheered as a child. He was Major League Baseball's youngest general manager (GM), topping that a year later to guide the team to its first World Series win in 86 years.

Now, one year later, that dream is over. For reasons that are still mysterious, Mr. Epstein walked away from a reported three-year, $4.5 million contract to do, well, no one's quite sure what.

Red Sox Nation, that group of fans across New England, the United States, and even overseas, uttered a collective groan. Here was an old-fashioned "Fenway fiasco," one of the worst things since the team famously traded Babe Ruth to the New York Yankees in 1919. That reaction says much about the changing perspective of baseball fans.

When GMs can become as popular as star players, it's a sign that bottom lines are becoming as important as bunts or RBIs. Chalk it up to free-agency and lineups that change every year. Or, maybe, thanks to "fantasy leagues," where fans assemble their own mock teams, it's every fan's dream to work the draft rather than swing the bat.

For whatever reason, the growing visibility of GMs coincided perfectly with the arrival of Epstein. Handsome and articulate, he brought glamour to the post as the most prominent of a new breed of young, highly educated baseball executives pulling the game into the 21st century. Days earlier, Epstein's own assistant, Josh Byrnes, 35, had been named the new GM of the Arizona Diamondbacks. He joins other boy wonders such as Jon Daniels, 28, GM of the Texas Rangers, and Andrew Friedman, 28, director of baseball operations for the Tampa Bay Devil Rays.

The role of GMs is magnified in today's baseball, says Andrew Zimbalist, an economist at Smith College and expert on the business of baseball. High player salaries make their decisions riskier, and they are subjected to ever more intense media scrutiny, he adds.

But Epstein "doesn't walk on water," Professor Zimbalist says. "He's certainly not infallible, and the Red Sox still have a bright future without him."

Epstein's surprising departure - apparently because of a dispute over his role in the organization, not money - may only add to his aura, baseball experts say.

"He got off the treadmill, and it's a fascinating decision, a fascinating turn of events," says Alan Schwarz, a senior writer for Baseball America. "Here's a clear case of someone for whom the money wasn't everything."

At a press conference Wednesday, Epstein only added to the mystery by refusing to pinpoint any specific reason for his departure and praising the Red Sox organization and his longtime mentor, team CEO Larry Lucchino. After considerable thought, he said, he decided he could no longer "put my whole heart and soul" into the job.

Epstein became famous for using esoteric statistics like "range factor," "park factor," and "runs created" to assess more accurately the value of players. Unlike pure statistics geeks, though, Epstein continued to lean on conventional scouting reports as well - in fact, longtime Sox head scout Bill Lajoie resigned in a show of support.

And though some other teams openly use the same principles - most notably the Oakland Athletics, profiled in the controversial 2004 book "Moneyball" - the Red Sox were the first team to win a World Series employing them. (Critics respond that the Sox's $120 million-plus payroll, second only to the New York Yankees, might have played a role in that success as well.)

Epstein "is one of the most extraordinary minds in the game, and I don't think his qualities are formulaic. He's most unusual," said Charles Steinberg, a Red Sox vice president, in a Monitor interview as the team's championship season began last year.

Along with the World Series win, Epstein convinced star pitcher Curt Schilling to join the team by eating Thanksgiving dinner at his home; snatched David Ortiz, an MVP candidate, from Minnesota for a song; and boldly traded Nomar Garciaparra, the team's most popular player.

Fan websites, blogs, and radio talk shows have become all-Theo, all-the-time outlets for a bruised Nation. "I think people see Theo Epstein as one of us, a local person who came from humble origins and got to live their dream of running a professional sports franchise," says Ron Sen, a medical doctor in Melrose, Mass.

Press interest grew so intense that Epstein was forced to escape from his office Monday disguised in a Halloween gorilla costume.