Despite a number of opportunities in the opposition penalty area, the reigning champions were unable to find a crucial away goal.
Instead, Didier Drogba found the net against the run of play to give the Premier League side an unlikely win.
"We knew that Chelsea always profit from the chances they create," Iniesta told TV3 Catalunya. "They had a few and we weren't good enough to finish ours.
"There's still the return leg to be played and we expect something similar to this one - they will put many men behind the ball.
"They defend quite well but we will be in our home with our people and that's always a big plus."
Barca host Real Madrid in La Liga on Saturday before welcoming Chelsea to the Nou Camp for the second leg of their European tie on Tuesday.