Gravity is at work as Roger Federer commences play in the U.S. Open, his 57th Grand Slam tournament.
Both in terms of physics -- what goes up must come down -- and the serious matter of any elite athlete forced to deal with growing older.
He has been so good for so long that his current No. 7 ranking sounds almost demeaning. At 32, despite his record 17 major titles, he lately has experimented with a new racket and fiddled with his pre-Open schedule. He admits to looking for answers among the hints and allegations that he may have won his last Slam event a year ago at Wimbledon.
"Overall," he said, "I'm looking at the big picture and just playing matches. I want to make sure I'm moving well and feeling fine. Some stats will never be great, but I've never been a big stat guy anyway. For me, it's important that I feel good at the end of a match."
Rafael Nadal, Novak Djokovic, Andy Murray and Juan Martin del Potro -- the four Slam champions who remain active since Federer won his first major title, the 2003 Wimbledon, and all ranked higher than Federer now -- continue to hold Federer in the highest regard.
Just last week, he reinforced that respect by battling Nadal on virtually equal terms through three sets in Mason, Ohio. But he lost. And everyone has known for a while: His unprecedented dominance couldn't go on forever.
"He's slowed down a little bit," said John McEnroe, himself a seven-time major champion. "The balance and the movement are not quite as Nureyev-like as they were in the past. So he's reaching for more balls and therefore mis-hitting more shots."
That 2012 Wimbledon title was Federer's only major crown in his last 14 Slam events, after having won a startling nine of his previous 15. He acknowledged feeling "a bit slower, you feel a bit weaker, you feel a bit softer, whatever it is" at times during matches. "You don't feel like Superman out there," he said.
What he is lacking, he said, is "a little bit of everything. I fell behind a little bit with injuries I've had. I think that just adds up over time and has maybe a little dent in your confidence."
Concurrent with slight doubts in Federer's mind is the encouragement his struggles present to opponents. "I, as a guy who was ranked 30 or 40," Patrick McEnroe said, "would think, 'Wow, Roger went to a different racket. Maybe I have a chance now. Maybe he doesn't believe in what he's doing.' "
Furthermore, Federer's options -- in terms of emphasizing aggressiveness -- appear limited, in Patrick McEnroe's mind. "He was never a high risk-taker," McEnroe said. "He was always a very meticulous player whose game was based on timing and movement, not just overwhelming like [Pete] Sampras. So now that his precision is a bit off, he's a lot more vulnerable."
Plus, John McEnroe added, "a part of why he's so great is because he's stubborn and he believes in himself, so he's unwilling to change a whole lot."
Meanwhile, he's not dead yet.
"It doesn't take much for things to go your way, all of a sudden," Federer said. "That's why you've always got to keep believing."