Obviously, the Serbian has spoken about retirement a few times in recent years. He's always had a pretty clear stance on the matter. He doesn't know when it will happen because it's not something that he'll ever settle on in terms of picking a date.
It will come when he feels like he can't be competitive in the way he wants to be anymore. That could be in five months- okay, maybe not in five months- but it could be in one year, two years, or maybe even three years.
We don't know, but Mats Wilander feels like he does kind of know, and he told Eurosport all about it.
"Pete Sampras retired because he was sick of tennis I think, there's a big difference. No, I think he's going retire when he doesn't feel like putting in the work. I think he will never lose the feeling and happiness of playing in front of 15,000 people."
"I think he will always enjoy that because he's such a warrior out there. But I think for him when you start losing a little bit, that is what’s really, really important to these guys."
Wilander didn't say anything we hadn't heard from Djokovic already. Part of being competitive, as Djokovic wants, is putting in the work it requires.
"But that's not the reason they're playing. They're playing to be competitive and to challenge themselves. But that starts with getting up in the morning and doing the work. And when that is not fun anymore, I think that's when Novak Djokovic will retire."
He's well known as a dedicated worker who puts hours into his craft, but sooner or later, that won't be enough. Perhaps even sooner, it won't be fun anymore, and that's when it will end.