Barcelona are hoping to seal an emergency transfer after Ousmane Dembele suffered a significant hamstring tear last week.
Dembele, who had already been out with injury since November, picked up a new problem in training and is now due to undergo surgery.
The 22-year-old will be out for the remainder of the season in a fresh blow to Barca, who are already without the injured Luis Suarez until at least April.
But LaLiga transfer rules dictate that teams can sign cover outside the transfer window in exceptional circumstances.
The Catalan club are working on signing a striker this week, with Real Sociedad's Willian Jose high up their wishlist.
They have also considered Luis Suarez (Real Zaragoza), Ante Budimir (Mallorca), Cristhian Stuani (Girona) and Loren Moron (Betis).
But how do LaLiga's emergency transfer rules work, and when do they come into play?
In order to bring in a new player while the transfer window is closed, teams are required to 'unregister' one of their injured players.
That player must be ruled out for a minimum of five months, while the team would need to inform LaLiga of the serious injury in question no more than 20 days after its occurrence.
In Barca's case, Dembele suffered his hamstring tear on February 3, giving them until February 23 to alert the League. With Suarez in contention to return in April, his injury is not considered severe enough to warrant an emergency transfer.
Dembele would instead be that player and, if 'unregistered', the French forward would not be able to feature for the remainder of the season regardless of whether he makes a miraculous recovery.
Once a team have decided to apply for an emergency deal, they must put their case to a medical commission, with a decision then made in the space of around three days.
Clubs may only sign emergency players from LaLiga or Segunda - or players who are currently unattached.
