The European champions were surprisingly held to a goalless draw with Rubin Kazan in their last game in the continental competition, to give the Serie A giants the chance to take the lead.

With second-placed Barca one point behind leaders Inter, Messi is convinced that only victory will be deemed an acceptable result.

"We have to win. And that's it. After losing points with Rubin," the Argentina ace told La Gazzetta dello Sport.

"We're forbidden from making any more mistakes at home. Otherwise qualification for the next stage would be really at risk.

"We have respect (for Inter), but sure we don't fear them. They are strong in all areas and have the ability to play several tactical schemes whilst in play.

"They have a great trainer in Mourinho, of whom you speak a lot."