Sunderland could find themselves in hot water after the collapse of Lamine Kone's proposed move to Wearside, with his current club, Lorient, to take the matter to the Federation Francaise de Football (FFF) next week, according to Sky Sports.
The two clubs agreed a fee for Kone before the player himself flew out to England at the beginning of the month to discuss personal terms and undergo a medical.
However, the proposed £5 million transfer would collapse, with Lorient claiming that Sunderland simply cancelled it and that Jan Kirchhoff's move to the Stadium of Light may have been a factor - though Sam Allardyce has claimed his team are looking to bring in two centre-backs, not just the one.
Regardless, the French Ligue 1 club are more than unhappy with the situation and have submitted a formal complaint to the FFF, which is to be sent on to England's FA and UEFA, according to NBC Sports.
Kone missed two games for his club because of the trip to the North-East, as well as three weeks of training because of France's break, and now Sunderland could face circumstances for their actions.
Sunderland to pay the ultimate price?
The grounds on which they cancelled the deal have not been disclosed by Sunderland themselves, so they may have a valid reason to avoid punishment if this does become a legal situation.
However, for now, NBC Sports have reported that there are a number of ways that the club could be punished, if found guilty - with one of those in the form of a points deduction, which would massively hinder the club's scrap for survival.
Four points from safety, the Black Cats need all the points they can get, and a deduction could well and truly send them down, depending on the severity.
Fines or a transfer embargo would certainly be the preferred penalty in that case, as Sunderland cling onto their Premier League status.
Black Cats defend actions
Despite Lorient's claims, Sunderland are standing their ground, with a spokesperson telling Sky Sports that they think the suggestion of legal action is "ludicrous" and that they will "vigorously defend [their] position" if it comes to that.
Allardyce has also been quizzed on the rumours of the club being sued, but he simply wanted to "leave" the situation alone whilst talking to the media this week, saying that the club "have already given a comment" about it and so there is no need for him to.
