Atletico Madrid's Filipe Luis said his team had to take on "everybody and everything" at the Nou Camp, claiming "there is a fear that Barcelona will be eliminated" from the Champions League.
Atletico lost Tuesday's quarter-final first leg 2-1, with goalscorer Fernando Torres sent off when they led 1-0.
Luis Suarez scored both home goals, but earlier appeared to kick Juanfran.
"I don't know what Barca players have to do to get sent off just like us," said Brazil left-back Luis.
"We had our chances, but we always knew it was going to be really difficult.
"They won, they have the result on their side, they had a lot of chances and, fortunately for us, they only scored two goals, so it could have been worse.
"We are still alive, we have to win now. It is possible, but it will be really difficult."
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Atletico scored a valuable away goal through Torres, but the game turned when the Spain striker was sent off for two bookings in seven minutes.
Atletico manager Diego Simeone was incensed by the decision of German referee Felix Brych, who seemingly missed Suarez lashing out at Atletico right-back Juanfran.
Luis agreed with his boss, adding: "We shouldn't have got the red card, it was totally unfair.
"It is not easy to play against Barcelona in the Champions League. We know it is really dangerous if they go out in the quarter-finals."
Simeone said he was not "angry" with Torres, though the former Chelsea and Liverpool forward later apologised.