Cadena COPE says issues between the board and predecessor Quique Setien could hold up Koeman's introduction.
The RFEF have not been able to process Koeman's registration due to Barca and Setién being in dispute over the former coach's contract settlement. As such, Setien remains registered as Barca's head coach.
There remains ten days for the bureaucratic problem to be settled.
But if it isn't, Koeman will be forced to watch the first game of his Barca tenure from the stands.