The man who hit Spain's World Cup final winner against Holland gave the Gunners a surprise leg-up for tomorrow's Champions League showdown.
He declared: "We are not a machine. It won't be easy. This isn't a walk along the promenade for us.
"But Barcelona never take the field looking to be arrogant. That would be an enormous error."
Yet midfielder Iniesta admitted: "People speak about the matches last year but things are completely different.
"No two games are ever the same and we are aware Arsenal will be very motivated this time. That makes them even more dangerous.
"Barcelona aren't invincible and going to London is risky.
"We can win the first match but we face a battle to stop Cesc Fabregas and a team which will want to show its very best against us."