Barca led on Saturday but could only salvage a 1-1 draw that handed Atletico a duopoly-snapping title - given Barcelona and Real Madrid had won the previous nine trophies in the Spanish top flight.
Iniesta hinted it was the end of an era at the Camp Nou as Barcelona endured a trophy-less season, saw coach Gerardo Martino depart the club, while captain Carles Puyol - who had given 15 years of service - also announced he was leaving.
According to Iniesta, conceding the title to Atletico meant it was time for an overhaul at the Catalan club, with his own future at the club - a place he has plied his trade for 12 years - even in question.
"We were relying on winning this game," the 30-year-old said.
"We haven't and that makes this season disappointing, because if we had won, everything would be different.
"The season is over, lots of things are over."
Despite signing a contract to remain at Barca until 2018, Iniesta remains on the radar of Premier League giants Manchester City, Manchester United and Arsenal, who are reportedly interested in luring him to England.
