MLB

B’day boy Jeter young at heart

Icons age. The baseball calendar waits for no one.

There is a fountain of youth of the mind, however, and Derek Jeter long ago discovered that secret of the game. No matter how he performs, good or bad, Jeter lives in the moment. He doesn’t worry about tomorrow. He doesn’t re-live yesterday.

He turned 38 yesterday, but the shortstop had the same mindset when he first became a Yankee. On the field he remains young at heart, and, often, in performance.

“I’ve always been pretty good of doing that,’’ Jeter said on a night he picked up two infield hits in the Yankees’ 6-4 win over the Indians at Yankee Stadium.

Is that the key to his success?

“I’d like to think so,’’ said Jeter, who leads the AL with 95 hits but is batting .247 his last 44 games. “I didn’t come in here today thinking about what I did yesterday. I don’t come in today thinking about what is going to happen tomorrow. It’s just what you can do on that particular day, otherwise I don’t think you could play this game because it’s a game of ups and downs and I’ve always tried to take it day to day.’’

Jeter is never thrilled to talk about age-related questions. As for all the birthday wishes, he pointed out, it’s “not grade school.’’

If birthday cupcakes were hits, though, Jeter would have 3,183. His next hit will tie Cal Ripken for 13th place.

When Pete Rose turned 38, he owned 3,170 hits. Rose went on to become the all-time hit leader with 4,256, retiring in 1986 at the age of 45.

Asked his perspective on having more hits than Rose at this point, Jeter responded in Jeterian fashion:

“I don’t think about it,’’ he said. “I try to figure out a way to get hits today. I’m not thinking about what’s happened in history or how many hits I have now, every single day you just try to do your job.’’

You never think about Rose’s milestone?

“Nope, not at all,’’ he said before adding with a smile, “unless, it could happen today. Could it happen today? I don’t think about it.’’

Not today, but perhaps someday.

At 38, Mickey Mantle was already retired for two years. At 38, Babe Ruth was in his next to last Yankee season. Ruth blasted 34 home runs and batted .301, but he would hit only 28 more home runs and 118 more hits in his career. The great Joe DiMaggio, like Mantle, retired at the age of 36. Lou Gehrig was 36 when he played his final game April 30, 1939. Icons age.

A scout at last night’s game said Jeter, “is still a winning ballplayer and can still make the difficult play at shortstop. His bat has slowed a bit, but in this lineup he is still such a productive hitter.’’

Jeter understands there is an end to the rainbow. A year ago at this time he was rehabbing a calf injury in Tampa. A lot of people thought he was done.

“I always knew you can’t play forever, especially here, when you have a lot of guys that come and go,’’ Jeter said. “A lot of guys I played with retired. Some come back. I’ve always understood that but I’ve never prepared for the end of something. I don’t sit around and think about when my last game is going to be.

“I never took anything for granted,’’ Jeter added. “I never assumed that just because I’m 30 that I’d be back playing the next year. I always had the mindset that you have to prove yourself and you have to go out, do your job. That’s what I’ve had since I’ve come up because of the Boss, when the Boss was here, if you didn’t play, he’d get rid of you. So that’s what my mindset has always been.’’

There is a fountain of youth of the mind.

kevin.kernan@nypost.com