The Spain midfielder was taken off at halftime in Thursday's King's Cup quarter-final first-leg win at Real Sociedad.
Iniesta, 32, is Barcelona's most decorated player alongside Lionel Messi but injuries have limited him to only six league starts this season. Barca have dropped points in five of the 12 games he has not started.
Barcelona midfielder Rafinha has also been ruled out of the trip to Eibar through injury while defender Javier Mascherano is suspended.
Luis Enrique's side are third in the standings, two points behind leaders Real Madrid but have played one game more than Zinedine Zidane's team.
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(Reporting by Richard Martin, editing by Ed Osmond)
