Roger Federer was a really amazing player in his day, but his longevity is not spoken about enough. In 2019, the Swiss ace was on the verge of beating Novak Djokovic in the Wimbledon final at age 38, which is amazing.
The way he was able to remain a basically dominant tennis player until a bad knee injury even when he was up there in age, is not seen often. Djokovic is certainly making a great impression of that as he's still arguably the most dominant player on the ATP Tour despite being up there in age, too.
He might even eclipse now-retired Federer by playing well into his 40s. We'll see, but if he does, then he might overtake the Swiss Ace for an interesting record.
Federer has the most ATP Finals appearances in tennis history with 17. The event began in 1970, and no player since then ever made it to 17 outside of him.
Novak Djokovic is right there, as this year's Finals will be his 16th. That's by far the most out of any player, as the next player up is Andre Agassi with 13. When you put all of that in perspective, it becomes pretty clear that Djokovic should get to number 17 next year.
If his health holds up next year, there is no way that he's not finishing in the Top 8 by the end of the year. He's too good for that and without any kind of crazy scenario, the Serbian is not losing that skill overnight.
It's not a record he's concerned much about, but the better the record the longer he was great, and that's certainly a goal for him.