A number of fans at San Mamés printed out fake money with the Barcelona logo on it and the word "mafia" in response to Barcelona's corruption charges.

Barcelona traveled to Athletic Club on Sunday for a crucial La Liga showdown, with the Catalan giants needing a victory in order to maintain a nine-point gap at the top over bitter rivals Real Madrid.

While the Lions have endured a drop in form, thus tumbling down the table, San Mamés remains one of the most difficult away grounds in the Spanish top flight. Fortunately for the visitors, they emerged with a victory, but it was a hard-fought result, triumphing by a mere one goal to nil.

Raphinha got the only goal of the game, netting just before half-time — though his goal was initially ruled out for offside before being awarded by VAR. However, while this result was brilliant, Barcelona boss Xavi Hernandez admitted to being unhappy with a number of things, one of which was the Athletic Club fans.

The Catalan giants received a hostile reception at the San Mamés and this was due to the league leaders' Negreira controversy. The Spanish giants have been charged with corruption after paying around €7M ($7.5M in today's market) to the company of Maria Enriquez Negreira between 2001 and 2018 while he was the vice-president of the CTA, Spain's Committee of Referees.

As a result, a handful of Bilbao supporters arrived at the stadium carrying fake money with the Barcelona logo on it and the word "mafia". Additionally, some fans could be heard chanting "to the second division", referencing a potential relegation as punishment. The Blaugrana, meanwhile, have not been found guilty yet and are set to fight their case, hence the frustration from Xavi. 

"It saddened me," the Camp Nou boss told Sport after the match.

"I respect the public of San Mames, they have always treated me very well. I am surprised by the hostile environment and it saddens me, I think that making judgements ahead of time is not good for society."

"We have not spoken in the dressing room, we are professionals. We hope to play football, to defend this team to the death," the 41-year-old also added.

It should be noted that the Liga leaders vehemently deny these accusations. Current president Joan Laporta wasn't named in the charges — former presidents Sandro Rosell and Josep Maria Bartomeu were, however — but has promised Culers that the club is innocent of any wrongdoing.

While Barcelona have acknowledged the money paid to Negreira's company, they claim that these were consultancy fees to aid their coaching staff in their matchday preparations. However, the Spanish public prosecutors refute this claim, arguing that the club made these payments in order to receive favorable decisions, both on the pitch and when selecting officials to referee the Blaugrana's games, which amounts to match-fixing.

If found guilty, the club could be barred from the UEFA Champions League, which will be a huge blow both on a sporting and financial level, with Laporta's side being in dire need of funds. Additionally, relegation from La Liga has also been mentioned but that would be the most severe outcome should the trial go ill for the Blaugrana.