Arsene Wenger claims even Uefa officials were 'shocked' by referee Massimo Busacca's decision to send off Robin van Persie in Arsenal's defeat by Barcelona.
Van Persie was dismissed early in the second half at Camp Nou for picking up a second yellow card after Busacca had deemed the Dutch striker had kicked the ball away.
The Arsenal forward had been flagged offside and fired the ball towards goal just a second after the whistle was blown, with Van Persie saying he did not hear it due to the noise inside the stadium.
He later described the decision as a 'joke' and Wenger was equally unhappy amid reports he confronted Busacca in the tunnel after the final whistle.
Wenger feels it was 'embarrassing' that Van Persie was sent off and does not believe Uefa's representatives were impressed by the referee's decision.
On his conversation with Busacca, Wenger said: "I think he must think he made the right decision."
He added: "I spoke to Uefa people. They are shocked as well because it killed a promising, fantastic football match.
"What for? If it's a bad tackle or a second bookable offence, okay, but frankly it is embarrassing."
The Arsenal boss continued: "Two kinds of people can be unhappy; those who love Arsenal and those who love football can be frustrated with the referee's decisions.
"When he made the decision it was a very promising game, very interesting. That's the regret.
"We lost against a very good Barcelona side, congratulations to them and good luck for the future.
"We have many regrets tonight because we didn't expect to lose the game like that. I feel sorry for people who watched the game."
Did Robin van Persie deserve to be sent off against Barcelona?