The nine-times European champions have a huge task on their hands in Tuesday's home second leg after Mourinho acknowledged they had been outplayed in the semi-final first leg in Germany.
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"I saw a team that was better than the other one, mentally and physically. The better team won today. I was very angry because the goals came again from our mistakes," Mourinho told reporters.
"We lose him [Lewandowski] for three goals - I don't know about the penalty - when we know exactly what he does," he added to Sky Sports.
"We know everything about him, the boy deserves credit, but we gave him big support."
The Poland striker scored in the eighth, 50th, 55th and 66th minute with a blasted penalty to leave an all-German final likely after Barcelona were humbled 4-0 by Bayern Munich on Tuesday.
"How did it go from 1-1 to 4-1, I really don't know. We lost easy possession and we couldn't cope with their counter-attacking. Many of the boys didn't perform," Mourinho added before a flash of defiance.
"We can [turn the tie around], it is of course very difficult but we can. In a crazy night where everyone performs at a high level. Of course we can," he said.
"I have learned that everything is possible in football. Everything can happen next week. If you ask my players if they can turn the game some will say no. In an hour more will say yes, and tomorrow everyone will say we can do it."
