Pete Sampras doesn't understand how Roger Federer does it. ''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. 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. ''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. More...