The Blaugrana beat their arch-rivals 2-1 at Camp Nou on Saturday evening to make it nine wins from their opening 10 La Liga games, yet Iniesta has insisted that they have room for improvement.
"We still have to hit top form. The team has to keep on improving over the season in order to be in the running for titles," Iniesta told Barca TV.
The Catalans hold a one-point lead over Atletico Madrid at the moment, while Madrid are already trailing by six points, but Iniesta has stressed that nothing has been decided yet.
"At this stage of the season it’s not definitive as there’s a long way to go. It’s true that matches against Madrid have something extra, an extra motivation," he added.
"On Tuesday [against Celta Vigo] there are another three points in play and if we don’t win that match, what we have done against Madrid won’t mean anything.
"We have to enjoy it and savour it, and then think about Vigo."