The controversial new Davis Cup format will likely be without some of the game's top names when the competition begins next year.
"No, I highly doubt [I'll be there]," Federer told reporters Thursday at the Shanghai Masters. "We'll see what happens.
"I don't think this was designed for me anyhow. This was designed for the future generation of players."
Djokovic expressed similar sentiments, citing "poor timing."
The Davis Cup competition will begin Nov. 22, 2019, after the official ATP season has concluded. Up until this point, the format was a 16-team draw spread out during the year, allowing players to drop in and out of the event as it progressed.
The decision to overhaul Davis Cup has been controversial from the outset. In late August, Federer voiced his displeasure in footballer Gerard Pique, accusing him of "meddling" with the tennis calendar.
Pique is the founder and president of investment group Kosmos, which spearheaded the Davis Cup makeover.
"The Davis Cup should not become the Pique Cup," Federer said at the time.
On Thursday, Djokovic said the timing isn't ideal, especially with the launch of the ATP World Team Cup set to begin in early 2020.
"I just feel like the date of the Davis Cup is really bad, especially for the top players," Djokovic said. "Between the two, I will prioritize the World Team Cup because that's a competition of ATP.
"But also I think and I hope that there will be a larger discussion between the players to understand how we are going to approach these two competitions."
Federer has not played Davis Cup since 2015, while Djokovic has competed in only two matches since the beginning of 2017.