When someone leaves, they say, you learn a lot about their character.
This not only applies to the person saying goodbye, but also to those who stay behind and look at the departing.
This is particularly evident in tennis icon Roger Federer, who has now announced his retirement as a professional.
As foreseeable as the decision was - for an athlete 41 years is an old age, and Federer was recently forced to take long breaks due to injury - it came as a surprise.
It didn't take long for reactions from his long-time companions and competitors to become public, confirming again how respected the Swiss is, not only in the tennis scene, how much he is admired.
Very few athletes, and Federer is undoubtedly one of them, manage to perform their skills so uniquely and make it look so easy that they are perceived as artists.
And that also from observers outside of the sports world.
The Roger Federer phenomenon
A literary memorial was erected a few years ago for what is considered by many to be the most elegant and influential player of the professional era.
The American writer David Foster Wallace, once an ambitious youth player himself and a fan of the white sport, already admitted in 2006 that he was an ardent admirer of Federer's art.
"Federer both flesh and not" is the name of his essay, which he wrote about the then 25-year-old star and which is part of his anthology on tennis, "String Theory".
The essay in the bilingual edition, published by Kiepenheuer & Witsch last year, is 50 pages long, after the Darmstadt tennis player Andrea Petković repeatedly pointed out the greatness of Wallace's text.
He's lucky.
The way Wallace approaches the Federer phenomenon in literature, describing his talent, his unique movements on the pitch and working out the beauty of his game, is not just "an homage" as the German subtitle puts it.
But also an artistic approach to the artistic side of tennis in general.