MELBOURNE, Australia (AP) -- Pete Sampras doesn't understand how Roger Federer does it. When he reached the age of 31, he was burned out from the grind of the tour, the constant travel. It was difficult to stay motivated.
That's why Sampras decided to walk away on top - after winning his 14th Grand Slam title at the 2002 U.S. Open.
''I was fatigued the last couple years,'' he said Friday at the Australian Open, where he'll present the men's singles trophy on Sunday. ''I feel like my last win (at the U.S. Open) was my last fuel in my tank. That's when I knew I was done.''
He's amazed that Federer is not only playing at the age of 32, but still trying to improve his game, adding Stefan Edberg as coach and switching to a larger racket.
''Seems like he wants to play for another four or five years,'' Sampras said. ''The fact that he's able to keep it so fresh is impressive.''
Since retiring, Sampras has not been a fixture at the Grand Slams. He plays a few exhibition events and he hasn't thought about joining his fellow rivals - Edberg, Boris Becker, Ivan Lendl, Michael Chang - in coaching.
''I still get in the gym. I work out a touch,'' Sampras, now 42, said of his post-tennis life. ''I play a lot of golf.''
But the American, who was the season-ending No. 1 for a record six straight years from 1993-98, said he was excited to return to the Australian Open this year to watch some tennis and reminisce about the big matches he played here.
Some memories are fonder than others. Even though Sampras captured the 1994 and '97 titles at Melbourne Park, he considered it one of the toughest slams to win.
''The Rebound Ace court they had at that time was tough on my body, tough to serve and volley on,'' he said. After playing Davis Cup late in the season, he also felt flat coming to Australia only three weeks later.
And then there was the quarterfinal against Jim Courier in 1995 when Sampras began weeping on court, overwhelmed with emotion after learning that his coach, Tim Gullikson, had been diagnosed with brain cancer. Gullikson died a little over a year later.
''The emotion in that match was very awkward, revealing for me to show that emotion,'' he said.
And although Sampras sometimes gets back on court for exhibitions, he won't be following Australian Pat Rafter's lead and entering the men's doubles at the U.S. Open. Rafter, who just turned 41, played in the Australian Open doubles this year with Lleyton Hewitt, losing in the first round.
''I miss the game, but I don't miss the stress,'' Sampras said.
He'll be rekindling one old rivalry in a few weeks, though, when he plays Andre Agassi in an exhibition in London.
''We battled for many years,'' Sampras said, diplomatically, when asked about his sometimes-tense relationship with Agassi. ''We're certainly very different - in every way.''