Tacchinardi, also a former Villarreal star, doesn't rate El Kun.
"The club are targeting a top player this summer," he told Radio Sportiva.
"However, I've played against Aguero and, in my opinion, he isn't one. He's just a good goal scorer.
"For me, a top player is someone like Samuel Eto'o at Inter, a man who can make the difference on the pitch and in the changing room."