He is 48 now, and it’s been a lot of summers since John McEnroe owned tennis in ways few others ever did, back in the last golden age of the sport, back when it seemed to matter in ways that it so rarely does anymore.

That is McEnroe’s legacy, even more than the memory of his sweeping left-handed serves and his brilliance at the net, even more than the fact that he and Bjorn Borg became the Ali-Frazier of tennis, one of the great rivalries in sports: McEnroe made us want to watch.

Hhe was like the comet streaking across the nighttime sky back then, a tennis version of the mad artist, all but howling at the moon as he painted his masterpieces. He was the breath of fresh air that went swirling through the dusty old corridors of what once had been called a country club, a style more suited to Shea Stadium than the U.S. Tennis Center next door, part great player, part bad boy, all wrapped up in a unique charisma.

And what were the odds back then that he’d still be playing competitive tennis, will be playing in Newport next week in the Gibson Guitar Champions Cup.

“Like slim to none,” he said. “Then again, I’m pretty much doing everything I thought I would never do.”

For what were the odds 20 years ago that McEnroe would become tennis’s unofficial ambassador?

Probably slim to none on that, too.

But that’s what McEnroe has become. An outstanding TV analyst. A former captain of the Davis Cup team. A former television talk show host. Still high profile in an era when many of his contemporaries no longer are, still heavily involved in the sport.

“I think it’s an important time for tennis,” he said. “Who would have ever believed 20 years ago that golf would be outdrawing it in the TV ratings. And not just golf? Poker. The X Games. Even bowling in some markets.”

He knows he came along at the right time, back when it seemed as if everyone was playing the game, new courts opening up, the sense that tennis was growing, attracting new fans, shedding its country-club image. McEnroe was at the center of that, no question about it, right there with Bjorn Borg and Jimmy Connors, back there when tennis seemed to be all about personalities.

He was the kid who had come out of nowhere back in 1977, when he was the unknown kid who came out of the qualifying round at Wimbledon and made it all the way to the semifinals before losing to Connors. Two years later he won the tournament and his world would never be the same again.

He would go on to win three Wimbledons and four U.S. Opens, and was ranked number one in the world for 170 weeks, but it was always more than that. It was the fact McEnroe became a celebrity in ways that must have once seemed unimaginable. Or how do you start out to be a tennis player and end up being under some microscope?

“The first two years were great,” he said. “Then you go from being the hunter to the hunted.”

He remembers when Borg told him that he was retiring, the moment that things started to change, “When everyone’s coming at you.”

McEnroe retired in 1992.

He was 33 then, had had a career he never could have envisioned back when he was just a kid growing up in Douglaston, Queens. But things were more complicated, too. His marriage to Tatum O’Neal was breaking up, and for the next year or so he rarely played. In fact, he began playing again simply to get in better shape and start feeling better about himself.

That was 13 years ago, and it’s not as if McEnroe started out to be the game’s unofficial ambassador. But somewhere along the way he just sort of morphed into it. Maybe it was a greater appreciation of what he’d accomplished as a player. Maybe it was simply getting older, getting remarried, being a parent, no longer the brash, young kid with everything ahead of him. Maybe it was all of it, realization that, in so many years, tennis was his life, and there still were things he could do with it, even if the glory years belonged to another time, a different era.

So he is still a presence in tennis, in the process of evolving into the game’s ambassador.

There’s a certain irony in that, considering that he always seemed such a rebel, always chafing at the constraints of the game. But maybe it’s this simple: most professional athletes never find a second act. McEnroe has.

Playing on the Champions’ Cup tour is just a part of it.

“I’m a perfectionist and I don’t like losing,” he said, “and this tour is not a circus act. We’re all playing to win.”

Although that gets harder, certainly. Many of the players he competes against are a decade younger. The clock doesn’t stop, even for John McEnroe on the senior tour.

But don’t misunderstand. McEnroe can still play, even at 48. Two years ago, he won the doubles in a tour event, making him the oldest player to win in 30 years.

He says he still loves to play, that in a sense it’s more fun now than it was in his prime, back when he was in the white-hot glare of the spotlight and the unrelenting pressure that came with that. As if he was almost too young then to appreciate it. And he also knows that he’s in the fifth set of his tennis life, that “my days are numbered out here.”

Which is reason enough to watch McEnroe play next week in Newport.

For very few ever owned the game the way he once did.

And maybe the biggest compliment you can give him?

Here it is 15 years after he retired, and no one yet has come close to replacing him.

breynold@projo.com