FORT MYERS, FLA. - Another year older, that's what Jamey Carroll is going to be thinking about today. They go by so fast. The skills have changed dramatically, and the body changes are noticeable almost by the day.

Yep, it's hard to believe his twins, Cole and Mackenzie, turn 5 already on Wednesday, isn't it?

But birthday balloons and pony rides are about the only thought Carroll will give to age, because his own doesn't seem to have any basis in reality. Carroll plays a position -- several of them, really -- requiring young legs, sharp reflexes, prime-of-your-career instincts. That he's displayed them all for professional teams for 18 seasons, and seems as adept and agile as when he began, defies the normal mathematics of aging.

"He's 39," says fellow infielder Brian Dozier, "going on 25."

Maybe so. Carroll had a typical season for the Twins in 2012, hitting .268, getting into 138 games and providing steady defense at three infield positions. By one measure, according to fangraphs.com's statistical base, Carroll was the Twins' most effective fielder except for Ben Revere, who is nearly 15 years younger.

It's a season that would be typical of a 28-year-old utility infielder. The sort that an intervening decade once made look impossible.

"It's impressive. With all the conditioning available to them now, maybe we underestimated how long guys can go, playing at a high level at those positions," said Paul Molitor, who defied age in a similar way -- he batted .341 for the Twins when he was 39 -- during his Hall of Fame career. "Jamey is about as professional as you can get, in terms of taking care of himself. Do your work in the winter, come here ready."

That's what Carroll does, not that it has anything to do with his age. "I'm training exactly the same way I always have. I haven't felt anything that tells me I'm older," said the Evansville, Ind., native. "I work hard for it. I always take the position that I'm the 25th man on the roster, so I don't take anything for granted. If anything, I try to overprepare."

But it's not so easy to prepare for the mental aspects of aging, for the knowledge that time cannot be defied forever. That's what amazes Molitor about the Twins' oldest player -- that his mind is as healthy as his body.

"All players have those mental battles. When you have a little bit of a tailspin, you start to wonder -- 'Is it a slump, or is this the descent?'"Molitor said. "That's the mental toughness part of it -- not only the grind, but maintaining the confidence to know you can still do it when a lot of people think you should be on the downside."

Far from wearing down, Carroll flourished as 2012 concluded. He batted .388 in September and October, the highest average in the American League. He'll earn $3.75 million this year, and the Twins can renew his contract for 2014 for $2 million.

Carroll is five years older than Josh Willingham, the Twins' next-oldest player. He's so old, the team that drafted him doesn't even exist anymore. (He's one of 14 remaining players who once wore a Montreal Expos uniform.) Yet he relates well to his teammates, even -- or especially -- with the infielders who are trying to steal his playing time.

Dozier, for instance, edged Carroll aside for the shortstop job last May, after the Twins decided to emphasize youth. Now the pair are fighting for the starting job at second base, and Dozier said his main competition likes to spend time helping him learn the position.

"Jamey and I are really close. He took me under his wing last year, and he helps me day by day," Dozier said. "Just the baseball knowledge, that's the only thing that's old on Jamey."