The Gunners crashed out of the Champions League with 4-3 on aggregate against the Spanish giants.
Wenger felt the decision to dismiss Robin van Persie cost the Gunners their place int he Champions League.
“We lost against a good team,” he told Sky Sports.
“In the first half we resisted the pressure. I believe that straight away in the second half it would have been very interesting if it had stayed 11 against 11. But that was not the case and at the end of the day we have many regrets.
“We were beaten by a terrific side, certainly the best team in Europe. I am still convinced that in the second half we could have done a lot at 1-1 if it had stayed 11 against 11.”
Referee Massimo Busacca decided to show Van Persie a second yellow card for allegedly kicking the ball away in the second half of the clash in Barcelona last night.
Wenger added on referee Busacca: “He must never have played in games of football of that importance, with people shouting.
“Even if he takes the chance, I don’t see why it was a second yellow card. He must never have played football at all to do that.”