Barca were forced to grind out a 1-0 win at Espanyol yesterday.
"We're doing well and we're confident, but we know how hard it's going to be. We are ready to fight until the end," said Alves.
"We never lost our intensity, our rivals play football too - they are playing for their lives in this competition, it makes it all very difficult. Barça may not win all their games comfortably, sometimes we can, other times we cannot."