Roger Federer (age 37), a three-player over 30-year-old D-Djokovic (age 31), Kevin Anderson (age 32) and a young ambition in the second round of the ATP final,
It fueled the debate about whether the younger generation is ready to challenge the highest honor yet.
However, Djokovic retreated, arguing that too much pressure was being placed on the heads of rising stars.
Federer overcame Dominique's team, and Anderson defeated Kai Nishikori yesterday and allowed Old Guard to dominate group Lleyton Hewitt.
However, Jockovich believes that his generation will soon be overturned.
"I know you guys are a little bit tough," Djokovic said.
"I think there is a lot of quality in the new generation.
"Zverev is definitely the next generation leader.
"He proved himself and set himself up as the best player.
"He has already won many Masters 1000 championships, and three of his career are quite impressive.
"The World Tour Finals must qualify for two consecutive qualifiers."
Djokovic listed three other players who might soon rank up.
"Then you [Karen] Khachanov, of course, [Stefanos] Tsitsipas, [Borna] Corrick. "
"I think tennis is in good hands.
"At the same time we think we are old people, and we are still working hard, working wisely and trying to make the most of what we have.
"I do not know how long I will go.
"Obviously, experience plays an important role in this kind of game: knowing the kind of approach, playing, acting at a certain moment, handling pressure and coping.