Atletico Madrid could find out on Monday whether they will have a FIFA transfer ban lifted, meaning they would be able to sign new players in the summer.
In January last year, Atletico and neighbours Real Madrid were banned from all transfer activity during the summer 2016 and winter 2017 windows.
The punishment was imposed after FIFA found they had broken rules on the international transfers of players aged under 16.
Both Atletico and Real appealed against the decision at the Court of Arbitration for Sport (CAS).
In December, Real had their punishment halved, meaning they can register new players from July 1.
AS reported that an Atletico party including director Clemente Villaverde, academy chief Emilio Gutierrez and lawyer Christian Keidel were in Switzerland on Monday to present their case to a three-man CAS tribunal.
Keidel has said his arguments would use the same premise that was successful for Real, which was that the Spanish FA was partly to blame for not explaining properly to FIFA that the youngsters involved were exempt from the rules because they had family and other links to Spain.
According to Marca, former Spanish FA secretary general Jorge Perez is among those who will testify for Atletico at the hearing.
The final decision will potentially have an effect on the futures of reported Manchester United target Antoine Griezmann and coach Diego Simeone.