Every now and then, Buster Posey manages to seem like one of the boys, just a ballplayer doing his job, doing it better than most, but not set apart or special, not a template of impeccability. Just as often, though, the Giants' catcher calls to mind the character of John Glenn in "The Right Stuff," the sublime screen rendering of Tom Wolfe's book on the Mercury Seven, the test pilots who became America's original astronauts.

Glenn's smooth perfection and aptitude with a microphone arouse suspicion among the others, who nickname him "the squeaky clean Marine." He wins them over with his response to an order to persuade his reluctant wife, who has a stutter, to allow Vice President Lyndon Johnson and the media into their home. Glenn phones his wife from the astronauts' training site and tells her, in a near-replica of a football pep talk, not to let any of them set a toe inside their house.

Posey could be baseball's squeaky-clean Marine. Strong-jawed and bright-eyed, Posey even looks a bit like a young Ed Harris, who played Glenn. He's not so fond of microphones, but the same pristine quality prevails.

A couple of years ago, as her son introduced himself to the big leagues and reporters kept contacting his parents in Georgia, Traci Posey puzzled over the fact that so many asked her to cite something Buster had done wrong. I explained that they were probably looking for a charming anecdote, like George Washington's cherry tree minus the ax and environmental carnage.

My then-colleague at the Chronicle, Scott Ostler, enjoyed recalling the time he walked past the indoor batting cages at AT&T Park, heard Posey get ahold of a pitch badly and shout in abject frustration … "Darn.''

At this point, nobody bothers trying to find the hacked cherry tree, the big flaw. They're just wondering what ordinary looks like on this 25-year-old.

He has won Rookie of the Year, Comeback Player of the Year, a batting title and the National League MVP in just 308 games as a major-leaguer. He hasn't played the equivalent of two full seasons, yet he has ridden in two World Series parades.       

By definition, his career so far is a modest sample size. Regression to the mean would temper expectations for Posey in 2013, but for all we know, he has barely begun to show what he can do. Caveats attach to each stage of his career: Rookie in 2010, injured and out for most of 2011, still recovering from the shredded ankle in 2012.

With all that, his mean is a .314 batting average, a .380 OBP, an .883 OPS, and a whole lot of ticker tape.

Yes, the ticker tape flows from the whole team, from great pitching, the sporadic brilliance of Pablo Sandoval, a closer somehow coming to the fore of Sergio Romo's slender body. But tell the people of the Bay Area that Posey isn't the linchpin. Just try.

San Francisco had never won the Series until his rookie year. Then he went down 45 games into his sophomore season, and the Giants floundered. He returned, and so did the Commissioner's Trophy.

That's not to say that the search for imperfections has been called off. His rapport, or lack thereof, with Tim Lincecum became a favored subplot last year. When he caught Lincecum's bullpen session at spring training in Scottsdale Wednesday and the two shook hands, news outlets in the Bay Area reacted as if they'd witnessed the fall of the Berlin Wall.      

The two spent most of the 2012 season apart as a battery, for whatever reasons. Lincecum started going bad and needed a change of scenery behind the plate. Posey, his ankle still tender, didn't need the hassles of chasing Lincecum's many deliveries in the dirt. Lincecum didn't trust Posey to get the stuff in the dirt. Bruce Bochy wanted Posey to take breaks from the squat and play first, so why not on the days of Lincecum's starts?  

In the end, it became too easy to cue up the theme to "The Odd Couple," casting the shaggy-haired Lincecum as the disheveled Oscar and the A-student Posey as the fastidious Felix. They are very different personalities, Posey living inside his head and guarding his words like plutonium, Lincecum seeking verbal catharsis when things went wrong, dropping an F-bomb on air after a division clincher and getting busted for pot possession. But they had adjusted to each other in 2010, and ended up sitting side-by-side at the post-parade celebration on the City Hall steps, the former Cy Young winner and future MVP chatting and laughing constantly like two kids acting out in class.

Posey addressed the crowd at that same celebration, pounding his fist on the podium as he said the fun could last for only a while, "then let's get back to work and make another run at it."

The 2012 postseason saw a slight drift from that seriousness. When he hit a grand slam during the Giants' comeback in Cincinnati, Posey briefly watched the ball in flight and then pumped his fist as he rounded second, wearing a sly smile. No one could suddenly confuse him with Bryce Harper, but the demonstration, even one this mild, surprised people accustomed to his containment.

"That boy Buster really has put his team on his back! That's the first time I've seen him show emotion," the Dodgers' Matt Kemp tweeted.

In the deciding game of the World Series, Posey hit a two-run homer and circled the bases with a finger held aloft in the rain. At this point, he seemed almost unrecognizable, except for the circling-the-bases part.

Many of his teammates had elaborate pet gestures to mark big moments, from a military-style salute to a pantomimed bow and arrow routine. They'd string some of them together every now and then, after a huge play and, as shortstop Brandon Crawford gleefully told Andy Baggarly of CSN Bay Area, "because I know Buster hates it."

Crawford is the same age as Posey, two months older actually, but on Posey, 25 years are tailored differently. He is as old as any ballplayer his age has ever been. He knows how to have fun, to share a beer with his teammates. But he also thinks working hard is fun. Not just a route to fun, but fun itself.

He would accept his MVP award while attending a $10-a-plate fundraiser in his hometown of Leesburg for the school where his mother teaches. She works with kids who have gotten into trouble with the law or failed to thrive in a traditional school.

The setting could not have been more perfect if MLB had set it up. And MLB wouldn't bother setting it up; it would be too hard to believe.

The whole premise of "The Right Stuff" was that the space program needed to craft heroes from accomplished, gutsy test pilots with an array of raw personalities. It was American mythology in the making.

That might be why so many reporters asked Traci Posey to cite a flaw. Her son doesn't seem entirely real, not as a personality, not even as a ballplayer, with all the numbers and trophies as hard evidence. We can't know what he'll do next, because we can still barely believe what he's already done.