Athletico's bid for Forlan suggests they are preparing for life without their captain Fernando Torres, who is Rafael Benitez's number one transfer target this Summer.
Liverpool have reportedly already offered Athletico £16m plus Luis Garcia for Torres but has been turned down as the Spanish side want the Reds to meet Torres' £27m escape clause.
"[Liverpool's bid was] insufficient - if you keep in mind that Fernando guarantees you 15 goals per year, especially when Nani, an unknown player, cost Manchester United £20m," said Torres' agent Antonio Sanz.