Atletico Madrid will have to put their transfer plans on hold after the Court of Arbitration for Sport (CAS) upheld FIFA's ban on the Spanish club.
Los Colchoneros and neighbours Real Madrid were both banned from registering players for two transfer windows in 2016 after being found guilty of breaching transfer regulations involving foreign players under the age of 18.
The Madrid rivals had each served the first part of their bans in January this year, although Los Blancos are free to do business as usual during the off-season after CAS halved their suspension upon appeal in December.
Atletico have not been so lucky, with the judicial body rejecting their appeal on Thursday, meaning that head coach Diego Simeone cannot bring in any new players ahead of the new season.
Antoine Griezmann has been heavily linked with a move to Manchester United, but the ruling is very likely to scupper any potential deal as Simeone is unable to replace the French forward – with Alexandre Lacazette and Diego Costa rumoured targets.
"CAS has dismissed the appeal presented by Atletico de Madrid against the penalty imposed by FIFA's Disciplinary Committee on the case of registering players under age and that was ratified by FIFA's Appeal Committee, reducing the financial penalty, but maintaining the prohibition of registering licenses in the next transfer market period," Atleti said in a statement.