All three players are due to play in the Paris Masters this week in what could be one of their final appearances all together at an ATP 1000 event.
Federer, 37, has already dropped a number of retirement hints and is not expected to play beyond the 2020 Olympic Games.
But Cilic thinks there will be a host of NextGen stars gunning to step into the shoes of the trio.
“When you look at what [Pete] Sampras did in the ’90s, few people thought players could beat his record,” Cilic said.
“It’s already done with Roger, Rafa, and Novak, so why can they not play at the same level?”
Meanwhile Cilic, a former world No 3, has only won five of his 30 matches against either Federer, Nadal or Djokovic.
And the Croatian knowns he has to improve his big-match performances if he is to add to his 18 ATP titles.
“I look at them always as positives and I am feeling the more times I am putting myself in positions to play against these top guys it is an opportunity to do well,” Cilic added.
“It is also an opportunity to learn about my game and what I have to do better in order to progress as a player.
“I felt that these matches in the past have been really good to me.
“There have been some tough loses but when analysing the game, analysing what I can do better in terms of trying to get better and performing on a consistent basis.
“Those games are challenging me always and making me lift my best game.
“In those kind of matches the top guys I am have to play and to the top of my performance level.
“That is also a challenging part to do it match after match and day after day.
“I feel the top guys are doing that throughout most of the year.
“They have small lapses of performance in the game itself and I am trying to do the same.”
Cilic has been seeded at the Paris Masters this week but he could still face Djokovic, Federer and Nadal, consecutively, in the latter rounds.
Source : EXPRESS