Precisely. Most great players decline precipitously in their early thirties. Agassi & Connors are the only exceptions in the Open Era - well, unless you go right back to Laver & Rosewall.
So what's the common link to play declining gracefully or little, and not precipitously?
I think the players who generally lasted longest are recognized as having outstanding footwork and desire to keep competing, along with the ability to stay relatively healthy.
Arthur Ashe rated Ken Rosewall
and Richard "Pancho" Gonzales
as having the best footwork in his day.
won his last title at the age of 43
in 1977. 3 weeks earlier he lost in the finals of the Sydney Indoors to Jimmy Connors.
Tony Trabert, who disliked Gonzales intensely, still had this to say about him: "Gonzales is the greatest natural athlete tennis has ever known. The way he can move that 6-foot-2-inch frame of his around the court is almost unbelievable. He's just like a big cat...". Gonzales won his last title 3 months short of 44
years old in 1972.
footwork and setup preparation are one of the greatest all time.
He won his last two tournaments at the age of 37
, and went to the semifinal in the US Open at age 39
Borg had outstanding footwork and speed and was one of the smoothest players ever to run on the court. But he didn't have the desire to continue playing beyond the age of 26
. I include him here as perhaps the best example of someone with superb footwork and athletic ability who did not have longevity due to lack of desire to compete further. One needs both.
Great footwork and preparation (similar to Connors), even though he didn't have the best speed. Won his last slam about 3 months short of his 33rd birthday (record still stands) and won his last tournament at age 35
is acknowledged as having one of the finest, most graceful (most efficient with little effort) footwork ever.
In my opinion, he is most similar to Mr. Gonzales in that respect.
Approaching age 31
, after winning Rotterdam 2012, he stated he has the desire to compete several more years.