The pair have played key roles for a Brighton side that finished sixth in the Premier League and qualified for the Europa League next season.
Mac Allister has been linked with a move to Liverpool after he also helped Argentina win the FIFA World Cup back in December.
Brighton rejected bids from Arsenal for Caicedo in the January transfer window, with the Ecuadorian later putting in a transfer request.
Although Caicedo made a surprise u-turn to extend his contract in March, the anticipation is that he has played his last game for Brighton.
"I think that can be the last game of Alexis and Moises, I'm really sorry," said De Zerbi after Brighton lost 2-1 to Aston Villa in their last league game of the season on Sunday.
"They are two great people and two great players."
"The policy of Brighton is like this," added De Zerbi. "I think it's right they can leave, can change teams and play in a level higher.
"We are ready. We have to find others big players to play without Alexis and Moises."
"If you ask me about Caicedo and Mac Allister, I love them and they are two big, big players and can be in a big, big European team," added De Zerbi.
"They can play in every competition and are ready to compete for a big team and I hope for them they can play in the best team in the world."
"For Brighton we can still improve [without them] and we can bring in other good players with the transfer market.
"Next year we will be playing in four competitions, the Premier League will be tougher for us for sure and we have to be stronger than this year.
"At the moment we are not ready to play three games per week, but we are not used to that. We will have to work in the transfer market and build a stronger squad with more players.
"The results we achieved were incredible, but we have the dream to improve these results."
