Ferrari confirmed Tuesday that Vettel would not remain with the team next season.
Sainz currently competes for McLaren, but his contract is set to end at the close of the 2020 season.
He drove for Toro Rosso from 2015-2017 but signed with Renault with four races left in 2017. He remained there through 2018 before switching to McLaren last year. Sainz’ best finish of third came in the 2019 Heineken Grand Prix of Brazil.
Ferrari has yet to announce the signing. Vettel hasn’t stated his future plans.