He was in contention for a Red Bull seat, with question marks over the form of Perez, but the reigning constructors champions elected to stick with the Mexican, and have extended his contract until 2026.
Sainz, who was a Red Bull junior driver and drove for the then-named Toro Rosso team (now Racing Bulls) alongside Max Verstappenand Daniil Kvyat 2015 and 2016, will not be making a return to the organisation.
Barretto has revealed the extent of talks between the parties, and it seems negotiations did not progress as far as some may have expected.
"The team evaluated in-form Carlos Sainz, who has won one race and taken three podiums so far this year, but conversations never accelerated to a point where they got serious," Barretto wrote.
Red Bull instead chose to keep faith with Perez, who has won five races with the team but struggled for consistency over his four seasons there.
It now seems inevitable that Sainz will have to accept a drive in the lower midfield, at least for 2025, as Mercedes appear set to back youngster Kimi Antonelli.