Zitat von Fifa-Regularien (RSTS)11. Unregistered players
Any player not registered at an association who appears for a club in any official match shall be considered to have played illegitimately. Without prejudice to any measure required to rectify the sporting consequences of such an appearance, sanctions may also be imposed on the player and/or the club. The right to impose such sanctions lies in principle with the association or the organizer of the competition concerned.
Ich verstehe das so: Bleibt Olmo bei Barca, darf er kein einziges Spiel mehr spielen. Da wäre es ziemlich unklug, wenn Olmo bleibt; außer Barca zahlt ihm eine Menge Geld dafür, was dann wiederum unklug von Barca wäre.