The Catalan giants lost more ground in Group C when they fell to a narrow 1-0 defeat at the San Siro.
Hakan Calhanoglu netted just before the half-time whistle to seal an important win for Simone Inzaghi's side, who have picked up two wins from three Champions League games.
Barcelona, meanwhile, were left seething after a number of decisions went against them throughout Tuesday's clash.
The biggest decision of the evening came late on, when the away side were denied what looked like a clear penalty when Denzel Dumfries touched the ball with his hand inside the box.
Despite evidence from replays, referee Slavko Vincic decided against giving a spot-kick; a moment that infuriated Barcelona boss Xavi and his players.
After the full-time whistle, a furious Xavi said: "I'm p***ed off by the situation we had to live through.
"It is an injustice, I already said yesterday that the referees would have to speak because I do not understand anything. He didn't want to give me explanations at the end of the game."
In addition to the questionable penalty decision, some believe Barca should have been given another penalty after a push on Robert Lewandowski, while many agreed goalscorer Hakan Calhanoglu should have seen red after a studs up tackle on Sergio Busquets.
Eduardo Iturralde, a former La Liga referee, made his feelings clear on the refereeing decisions on Tuesday night.
"There is an extremely clear red card on Calhanoglu for his tackle on Busquets," he said via @BarcaUniversal. "There are two penalties not called, one for handball, the other one after pushing Lewandowski. I know that sometimes you can make mistakes, but this..."
Wrong decisions from the referee tonight:— Barça Universal (@BarcaUniversal) October 4, 2022
- Penalty not called for handball by Dumfries
- Penalty not called for pushing Lewandowski
- Red card not given to Çalhanoglu for his tackle on Busquets
Spanish publication AS claim Barcelona will now make a formal complaint to UEFA through its legal services.
The complaint will include images to show what they believe to be a "flagrant act of injustice". They also suggest the Spanish club will ask that Pol van Boekel, who was in the VAR room on Tuesday, to never be involved in a Barcelona match again.
Barca currently sit in third place in Group C with three points.
"We now have three finals to play," Xavi said after the final whistle. "We are in an uncomfortable position. They have six points, we have three, and Bayern have nine.
"We had our chances but we couldn’t take them and they scored with a shot from distance – we knew that was one of their strengths."
🎙️🚨| Xavi: "I'm angry & I believe the result is UNFAIR, that's why yesterday I said the referees should go out and speak to the media. I asked for explanations after the match but he refused to give me any explanations." #fcblive #InterBarça #UCL 🔵🔴 pic.twitter.com/MLtM4V9t1K— BarçaTimes (@BarcaTimes) October 4, 2022
Thoughts on the decisions?
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Featured Image Credit: Twitter/@Zona_Blaugrana
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