Mets ace Tom Seaver pitches in World Series Game 4...

Mets ace Tom Seaver pitches in World Series Game 4 against the Baltimore Orioles on Oct. 15, 1969. Credit: AP

An old man has dementia, sad but unremarkable news in the course of human events. Godspeed to him and his family.

But of course it is more complicated than that when you are a public figure, in particular a beloved sports or entertainment figure, in particular such a figure from one’s youth.

In particular: Tom Seaver.

Such people share a piece of themselves with the rest of us. That is what makes the kind of news that Seaver’s family delivered Thursday not just about the person affected and his loved ones but about the rest of us, too.

Everyone has them, sports fans more than most: someone you followed at fandom’s formative age whom no future jock ever can quite replace.

In my case, it started in a tiny sliver of New York sports demographics, slightly too young to remember the Jets winning Super Bowl III and just old enough to remember the late summer and early fall of 1969.

My father died in 1967, with no known sports fan affiliation. I was a blank slate, waiting for someone to fill in team colors. Along came the ’69 Mets, Seaver the first among equals. So, orange and blue. Done.

Tom Seaver

MLB seasons: 20

MLB teams: Mets, Reds, White Sox, Red Sox

Record: 311-205 (.603)

ERA: 2.86

231 complete games

3,640 K in 4,783 innings

Awards: NL Rookie of Year (1967), NL Cy Young (1969, 1973, 1975), World Series champion (1969), Hall of Fame (1992)

I attended my first big-league game on July 27, 1970, and saw him strike out Willie Mays three times. I was at his 300th victory, in 1985, at Yankee Stadium.

I spoke to him in 2007 about Tom Glavine’s 300th victory, and he seemed fine. I spoke to him in 2012 and again in 2013, and he did not seem fine.

Now this.

Again, he is just one man, with troubles like any other, and his fans of a certain age are no different from other fans of other ages in other cities with other sports favorites from their youths.

Tom Seaver

MLB seasons: 20

MLB teams: Mets, Reds, White Sox, Red Sox

Record: 311-205 (.603)

ERA: 2.86

231 complete games

3,640 K in 4,783 innings

Awards: NL Rookie of Year (1967), NL Cy Young (1969, 1973, 1975), World Series champion (1969), Hall of Fame (1992)

But this one comes with an extra dollop of wistfulness because it happened during a 16-month stretch in which we will be celebrating the 50th anniversaries of the Jets, Mets and Knicks winning their first championships. (They have totaled only two more in the half-century since.)

Fiftieth anniversaries always are precarious, teetering between nostalgia and history.

Celebrate a 25th anniversary — think 1994 Rangers — and most people are old enough to recall what happened, with the players still looking mostly as we remembered them. Celebrate a 75th and well, no.

In between it gets fuzzy, like our memories.

The Jets, Mets and Knicks of 1968-70 who still are with us are mostly in their 70s now, many still vibrant, others not. This will be their last major go-round in the spotlight.

Some perspective: If I were to tell a current 9-year-old about the 1969 Mets, it would be the equivalent of an old-timer telling me when I was 9 about the Black Sox of 1919. Fifty years is a long time.

Back to Seaver. He could be cocky and cranky, not that there’s anything wrong with that. The Mets needed it back then.

They traded him to the Reds in 1977, still one of the most shocking developments in New York sports history. Later, he worked in television booths for Yankees and Mets games, covered some World Series, made wine, became an elder statesman, threw the ceremonial last pitch at Shea Stadium.

But the news that he no longer is up to public appearances did not come as a shock to those who have been around him recently.

Joe Namath and Walt Frazier carry on, seemingly in good health, the latter going strong as the Knicks’ lead television analyst. So all is not lost for those of us in the dwindling ranks who remember their glory days.

And we still have Seaver, too. His own memories are damaged by his condition, but the ones he left for the rest of us carry on.

Newsday LogoSUBSCRIBEUnlimited Digital AccessOnly 25¢for 5 months
ACT NOWSALE ENDS SOON | CANCEL ANYTIME