The Blues proved Barca's nemesis once again on Wednesday night as they won 1-0 in the Champions League semi-final first leg at Stamford Bridge.
That was despite the visitors dominating almost every aspect of the game from an attacking perspective, leading midfielder Iniesta and even the club's own website to lament what they perceived as an "injustice" and substitute Pedro to say: "We looked like fools when they scored."
But Barca - who had won 11 successive matches prior to Wednesday - only had themselves to blame after wasting a glut of chances to score, with the profligate finishing that has dogged them at times this season returning with a vengeance.
"That is the only thing that leaves a bad taste in the mouth - the failure to score," Iniesta said.
"We generated enough chances to have won the game.
"But we can't feel sorry for ourselves - what we have to do now is think about the games that lie ahead."
The first of those games is Saturday's potential Primera Liga title decider against Real Madrid, who lead Pep Guardiola's men by four points going into 'El Clasico'.
That is followed by Tuesday's return leg against Chelsea, a four-day period that will determine whether the Club World Cup, UEFA Super Cup and Spanish Super Cup winners are still on target to triumph in every competition they have entered this season.
Becoming the first ever club to retain the Champions League crown is the number one goal and Iniesta was under no illusions about what they would have to overcome to reach their second successive final.
"We expect them to sit deep and wait for us, playing on the break," he said.
"We will have to be very aggressive when it comes to trying to create chances and to attacking them.
"We have to be careful, though, because the result is a difficult one. We have to have the same mentality."
Chelsea's uber-defensive tactics on Wednesday split opinion between the purists and pragmatists but Iniesta had no problem with that type of approach, something Barca are long used to having to overcome.
"They have to try to take advantage of their strong points and that is fine," he said.
"They have to do what their think is in their interest, playing to their strengths. We do the same thing."
Feted by many as the best club side of all time, Barca still have weaknesses they have not addressed this season or beforehand.
Victor Valdes is a superb sweeper but his feeble attempt to keep out Didier Drogba's shot on Wednesday once again highlighted his failings as a goalkeeper.
Valdes said: "Chelsea were 100% effective - they scored from the only chance that they had.
"It is a shame but we can only trust that if we play the same way in the second leg, we can still go through. 1-0 away is always a very dangerous result, though - and we know that."
He added: "We gave everything and stood up to be counted.
"We played the way that we wanted to play, the way that we had planned and the way that coach asked us to.
"If you look at the number of chances that we made, we can feel reasonably pleased with our performance.
"In the second leg, we have to make chances and we have to take them. That is the key.
"The players leave here with their heads held high.
"We are confident that we have a chance of going through after the second leg."