NEW YORK - Roger Federer’s rivals weren’t exactly writing him off. Not publicly, anyway.

Still, plenty of people were, and he heard them. Federer delivered a response with his fifth consecutive U.S. Open championship and his 13th career Grand Slam title, moving within one of Pete Sampras’ record of 14.

The response amounted to this:

Don’t for a minute think I’m done.

Don’t for a minute think I’m going away.

Don’t for a minute think I won’t be collecting more of these titles.

His play delivered that message at Flushing Meadows — particularly in one-sided victories over Novak Djokovic in the semifinals and Andy Murray in the final. Then Federer went ahead and articulated it Tuesday when asked how long he can continue to win major tournaments.

“I have the belief right now that I can do it as long as I’m healthy, really. That’s the way I feel. I’m going to believe till the end of my tennis days that I probably can win a Grand Slam,” he told a small group of reporters at the Empire State Building. “And if it’s not the case, or I don’t believe in it anymore, then I’ll probably retire.”

Here’s the really bad news for men with designs on winning Grand Slam events: Federer is healthier than ever.

Not only is his bout with mononucleosis a distant memory, but his extra dedication to taking care of his body is paying dividends.

“What I’m striving for is longevity. ... I feel so much better physically today than I ever have. I mean, like, maybe this year was difficult, but right now, the day after the U.S. Open, I feel like, ’My God, I’m fresh,”’ Federer said. “I don’t have these niggling injuries any more like I used to have when I was younger. I remember I had a sore arm every day when I was 20, 21. I had muscle pain all over my body after, like, a four-setter.”

He mentioned, as he has in the past, that he intends to compete at the 2012 London Olympics — tennis will be contested at his beloved All England Club — and beyond.

And why not?

He’s still only 27, and unlike U.S. Open women’s champion Serena Williams, who doesn’t hide her interests in fashion and acting, Federer can be heard to say, “I live and breathe tennis,” as he did Tuesday.

“I feel, for a very long time, that I’ll always be able to win Wimbledon, always going to be able to win the U.S. Open,” Federer said, his latest silver trophy sitting inches away on a table. “The first thing that’s probably going to go is the French Open, even though I think that should also not be a problem, you know — having a shot there — because I’m such a good all-arounder and I’ve proven myself so much over the years there.”

Ah, the French Open.

It’s the one real gap on his resume, although he also listed leading Switzerland to a Davis Cup title and winning an Olympic gold medal in singles among his “many dreams” as yet unfulfilled.

Unlike Sampras, who only once made the semifinals at Roland Garros, Federer reached the past three finals there, losing each time to four-time champion Rafael Nadal. Nadal, of course, also stopped Federer’s reign at Wimbledon and recently ended his 4½-year stay at No. 1 in the rankings.

At least Federer can joke about his French Open history.

As he and Murray posed for postmatch pictures Monday night, one with the champion’s prize and the other with his runner-up dish, first-time Grand Slam finalist Murray asked whether Federer gets to keep the trophy.

So Federer explained that the U.S. Open replica trophy is the best of the lot because it’s the same size as the original. What they give you at Wimbledon is only 75 percent as big as the real one, he pointed out, and the one at the Australian Open is quite small.

But, Federer recounted, smiling at his own punchline, “I told him, ’I don’t know about the French Open.”’

Later, Murray said he figured Federer probably has at least four years left “right at the top.”

Video   Federer celebrates big win Sept. 9: TODAY hosts talk to tennis champ Roger Federer about taking his fifth win at the 2008 Men’s U.S. Open. Today show

“It depends how much everybody else improves, I guess,” Murray said. “He’s still playing great tennis, but, I mean, I wouldn’t be surprised at all if he did overtake Sampras.”

If Federer wins the Australian Open for No. 14, the pursuit of record-breaking No. 15 would begin at the French Open, of all places.

But instead of looking ahead to that, let’s look back for a moment.

Until Monday night, everyone seemed concerned about Federer. About his game, about his health, about his mental state.

Everyone, that is, save Federer himself.

“I never really had any moment where I was like, ’Things are just not working out for me,”’ he said, “because at the big tournaments, I actually did play very well.”

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