Of the top 100 men's tennis players, one is 37, three are 36 and the rest trail behind all the way down to the two 19-year-olds Denis Shapovalov and Alex de Minaur.
They are respectively No 28 and 45 and are on the rise.
This week's events at the US Open raise a familiar question, the more so when you realise that the guy at 37 is the world's No 2 ranked player. So once more into the breach: should Roger Federer walk away in the wake of his loss to Australian John Millman, a respectable journeyman, in the round of 16 in four sets in New York?
From this corner Federer can do whatever the heck he likes, his record of achievement won't be tainted, even if he carries on and starts losing regularly to far lesser players. His greatness, his significance on the game won't change. But it will become sad viewing if that's what unfolds, a case of striving against the dying of a once peerless game.
He's clearly still enjoying himself, otherwise why carry on.
Three names to ponder: Mark Spitz, Bjorn Borg and Nico Rosberg. They have one thing in common: they got out at the peak of their powers, although each was distinctly different in how they did it.
American swimming star Spitz held 10 world records going into the 1968 Olympics, but won just two team golds. He made up for it in Munich in 1972, splashing to seven Olympic golds, then retired at 22. He foolishly tried to come back at 41 for the 1992 Olympics - encouraged by a million-dollar offer if he qualified for Barcelona by documentary maker Bud Greenspan - and you can guess the outcome of that.
Borg won 11 grand slam titles - six French and five successive Wimbledons - before walking away at 26. He mightn't have liked the look of an upstart, shouty American making his way to the top and could see into the future and didn't fancy the view with John McEnroe at the top of the hill. Borg made one laughable comeback 10 years later with his trusty wooden sticks, confident they still possessed magic powers, and was predictably blown away by the modern lightweight graphite rocket launchers.
Rosberg won the Formula One championship in 2016, and retired five days later, marbles intact, at 31.
So what goes through Federer's mind at this stage of his career? He looked knackered against Millman, not surprisingly considering the heat.
He's up to 20 grand slam titles, four clear of Rafael Nadal, but that lead might be whittled by the end of the Open.
Seven years ago someone very close to this chair suggested Federer should start thinking about retirement. The clock was ticking, yada yada. What did he know.
Still the thought now resonates more sharply than it did then. He can still beat most players, on most days, but is that enough?
Bottom line: it's the Swiss master's choice, and only he really knows what's going on up top.
Oh yes: the other oldies in the top 100? The 36-year-olds are Julien Benneteau of France at No 60, Feliciano Lopez of Spain at No 63 and Paolo Lorenzi of Italy at No 94.
No 2 at 37. That takes some doing.