The Spanish side needs to win agains the Croatians if they are to go through to the knockout stages of the Europa League.
Valero said: “We need to win the game no matter what. Teams cut here to shut us out, but we are used to it and we must take our game to them in order to win.
“They are in good shape and it will be difficult, but if we score an early goal it could solve the game.
“We have two very fast forwards who can do them harm.”