Barcelona coach Xavi Hernández pleaded with LaLiga referees to "let us compete" and claimed the Catalan club are "paying for the Negreira case" after Vitor Roque's red card in Saturday's 3-1 win at Alavés.
Roque was sent off just 13 minutes after coming on for picking up two bookings having also scored Barça's third goal, with the second caution especially debatable.
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Xavi complained it is one of many decisions to go against Barça this season and suggested his team are seeing the consequences of the investigation into their relationship with the former vice-president of Spain's refereeing body, José María Enríquez Negreira.
Barça paid companies linked to Negreira over €7 million ($7.6m) across 18 years, but maintain they were purchasing technical reports into refereeing and never bought match officials or influence.
"It's a refereeing error against us -- it's just an unfair dismissal, if we are being honest," Xavi, who said Barça will appeal the red card, said in a news conference.
"I just ask the referees to let us compete in LaLiga. This is another case of a clear mistake against Barça. Everyone can see the reality.
"We are paying for the Negreira case, absolutely no doubt. But that's it, I am not going to speak about referees anymore."
Xavi's comments come just 24 hours after he accused Real Madrid TV of "influencing the competition every week" by broadcasting videos highlighting refereeing mistakes before and after games this season.
That prompted Madrid coach Carlo Ancelotti to say he would not sink to Barça's level after the Blaugrana president Joan Laporta also said Real Madrid "are not behaving well" in an interview on Friday.
"I have a good relationship with Ancelotti," Xavi responded. "This is not to do with him. I have complete respect for Ancelotti."
Roque's expulsion took the shine away from what should have been another encouraging performance from the Brazilian, who scored his first goal for Barça in the 1-0 midweek win over Osasuna.
The 18-year old came on in the 59th minute, cooly scored Barça's third goal in the 63rd minute, was booked in the 67th minute and then sent off in the 72nd minute for a supposed foul on Rafa Marín. VAR cannot intervene to overturn yellow card offences.
Barça had earlier led 2-0 thanks to two good team moves culminating in goals for Robert Lewandowski and Ilkay Gündogan.
Striker Samu Omorodion had briefly got the home side back in the game, but Roque's goal sealed the points for Barça and moved them within seven of leaders Madrid, who play Atlético Madrid on Sunday.
"It's always positive to win," added Xavi, who announced last weekend he will step down at the end of the season. "After my decision, that's back-to-back wins, so there's the team's reaction for you.
"Alavés had chances, but we were clinical, which is what we have lacked this season. We were good with and without the ball and it is a result that strengthens us in the fight [for LaLiga]."
Xavi also praised the displays of Andreas Christensen, who stepped up from defence to play at the base of the midfield, and teenager Lamine Yamal, who once again impressed on the right wing.
"Lamine is a brutal talent," Xavi said. "Very few players appear with his quality. He has it all, plus he works hard for the team, battles, helps the fullback and is humble.
"He is only 16, but he is brutal natural talent. We are in the face of something special."