Club captain De Ligt completed his long-awaited move to Serie A champion Juventus on Friday, as the Italian side paid an initial €75 million ($120.7 million) with the deal including a further €10.5 million ($16.9 million) in add-ons.
Ajax has wasted no time in splashing some of the cash on 21-year-old Mexico international Alvarez, who will come in from America on a five-year deal for a reported €15 million ($24.2 million) fee.
The Dutch giant, which has also lost Frenkie de Jong to Barcelona ahead of the 2019-2020 campaign, confirmed central defender Alvarez will arrive subject to a medical.
Ajax, the winner of a domestic double last term as well as reaching the semi-finals of the UEFA Champions League, said in a statement Alvarez can also play at right-back or in midfield.
Alvarez is the latest new face for Erik ten Hag's side, joining players including Quincy Promes, Lisandro Magallan, Lisandro Martinez and Razvan Marin in signing for the new season.