The Spain international picked up the injury during the first half of Wednesday night's 2-2 draw against Real Madrid in the Copa del Rey at Camp Nou and had be replaced just before the half-hour mark by Pedro.
Barca initially revealed via Twitter that the player had sustained a thigh problem but it was discovered after tests at the Ciutat Esportiva Joan Gamper on Thursday that Iniesta had suffered a minor hamstring tear and is now facing three weeks on the sidelines.
The Catalans will now be without one of their key performers for not only the upcoming Primera Division clashes with Villarreal, Real Sociedad and Osasuna, but also the first leg of their Champions League last-16 tie with Bayer Leverkusen.
Worryingly for Iniesta, this is the fourth time that he has been injured so far this season.
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