Novak Djokovic is picking up years at the same rate as everybody else but he seems to be capable of playing tennis for a few more years according to Mats Wilander.
Djokovic is one of the best players in the world and despite pretty much all of the top 10 being younger than him he's still among the best of them. The Serbian simply knows how to plays tennis and uses his skill to counter the energy and athleticism his opponents bring to the game. Even so he's among the better athletes on the Tour even at this age and he'll certainly be able to compete for a few more years if his health serves him.
According to former player Mats Wilander who knows how taxing the sport is, Djokovic could play until he is 40 years old:
"When you talk to Novak, he's so humble these days. I actually think that is the main reason why he is able to keep going, because he does take it day by day. I think he can play until he's 40 years old, he looks so young and is so fresh. He's keen, he's motivated - even in interviews with me!"
The biggest obstacle for Djokovic at this year's Roland Garros will be finding a way to overcome Carlos Alcaraz. Some would say Alcaraz is as equally good as the Serbian and a lot younger. On that matchup, Wilander said:
"I think if Alcaraz plays his best tennis, I think that it would be very difficult for anyone to beat him. But you have to make him play worse, and I think Novak Djokovic is one of the few guys that can actually, somehow, make Alcaraz doubt himself, make Alcaraz come up with unforced errors which he doesn't do against other players. He [Djokovic] is going to get five matches before he runs into Alcaraz - that's enough practice for Djokovic."