Robin van Persie has labelled referee Massimo Busacca "a joke" after his red card in Arsenal's 3-1 defeat to Barcelona.
Van Persie was shown a second yellow card in the 56th minute of the game for kicking the ball away. The Gunners had held an advantage at the Camp Nou at the time of the dismissal after Sergio Busquets' own goal made it 1-1 on the night.
Barca took full advantage of the extra man as Xavi levelled the scores on aggregate before Lionel Messi converted a penalty when Pedro was brought down by Laurent Koscielny.
Asked if the sending off had a significant impact on the result, Van Persie told Sky Sports: "I believe so. I think it had a big influence. It was a total joke, the sending off, because how can I hear his whistle with 95,000 people jumping up?"
When it was pointed out that there was just one second between the whistle and Van Persie's shot, the striker replied: "Makes it even worse. This way - one second from his whistle to my shot - makes it even worse.
"If there were four, five, six seconds in between, you can make a check [for offside]. One second, it's a joke.
"It's just a joke. He's been bad all evening. He's been a joke all evening, whistling against us. I don't know why he's here tonight. I think it's a joke."
He added: "We feel betrayed a bit. When it was 1-1, it was all to play for, and in my opinion the ref killed the game."
With Arsenal failing to register a shot on target during the game, Arsene Wenger accepted that Barcelona had been impressive but stressed that the decision may have had a significant influence on the outcome.
"We lost against a good team," he said. "In the first half we resisted pressure - I think the second would have been very interesting if we had stayed 11 against 11. Unfortunately it was not the case.
"There are regrets when you see how we went out - the way we did, it is very difficult to accept."
On Van Persie's second booking, he said: "With the people shouting, if he takes his chance I see no reason to give a second yellow card. To do that, [the referee] must absolutely have never played football.
"I told him what I think about his decision face to face and there is not a lot more to say."
Pep Guardiola said he could understand the anger over the dismissal but emphasised that his own team's performance had been decisive.
"Arsenal defended very, very well but they didn't make more than three passes [in succession]," he said. "It was difficult with ten against 11 and after the situation with the second yellow, I can understand the reaction.
"We created a lot of chances, we played a perfect game. We're so, so happy about our performance. Over the two legs, we were better than them."