Aguero left for Manchester City last week and Atletico plan to use the €45 million from his sale to land a top class replacement.
Falcao is their top target, says AS, despite the Colombian penning a new contract.
The striker's buyout clause is now €45 million, however he has an agreement with Porto that he can leave for €35 million.
Atletico plan to reduce the fee further by including attacking midfielder Eduardo Salvio in their bid. The Argie spent last season on-loan at Benfica.