Atletico Madrid president Enrique Cerezo labelled FIFA's transfer ban against the club as a "huge injustice".
La Liga side Atleti and their city rivals Real Madrid were banned from registering new players for the next two complete transfer windows on Thursday.
FIFA's Disciplinary Committee ruled that the capital clubs were in breach of regulations "relating to the international transfer and registration of players under the age of 18".
However, both teams were quick to launch an appeal against the sanctions.
And Cerezo says the punishment came as a surprise, telling AS: "We are completely in the right.
"We never expected this sanction. It's news to us. It's a huge injustice and not being able to sign players is a problem, but we've got a strong squad.
"We are studying all the documentation FIFA have sent us. We have to read all 110 pages."
Barcelona were hit with a similar punishment in April 2014, although a series of appeals meant their sanction did not begin until January 2015.