Due to an administrative error made by Ajax, the striker was not registered on the list of players for the Europa League, which had to be submitted no later than Tuesday, February 2. Haller, who joined from West Ham United to Ajax on January 8, can be used in Eredivisie and cup matches.
Despite attempts to rectify the error and make Haller available, the club received a definitive message from UEFA on Thursday evening that Haller will not be allowed to play. Oussama Idrissi, another forward who joined Ajax in the last transfer window, can be used in the Europa League.