"It didn't go well. With all the players suspended, I thought a draw would've been a good result, but it went this way," said the Brazilian.
"It is possible we didn't see the right approach, as after the final whistle the Coach told us our attitude has to change. Now we will prepare for the next Serie A and European game, we have to improve.
"Mancini was angry, but we all were, as nobody likes to start the Champions League with a defeat. It's only right he was cross with us."
Julio Cesar added: "Last season we had a bad start as well, losing our first few games, but we qualified anyway and so must carry on with our heads held high.
"We have a very strong squad and with these players, we must always believe in our potential.
"I think that the Coach can better explain what went wrong tonight, so I don't like discussing these things."