The Barca captain strained a calf muscle in the first half of Barca's 1-0 win at Real Sociedad in the King's Cup on Thursday, the third injury he has sustained in a season in which he has only started six league games.
Luis Enrique said Iniesta would not be out for long although local media said he would also miss at least two more games after Sunday.
Even at 32, Iniesta remains vitally important to third-placed Barca who have dropped points in five of the 12 games he has not started.
Luis Enrique said he has tried to restrict Iniesta's playing time to keep him fresh but appreciated that his team are never quite the same when their diminutive midfielder is away.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"There is no-one like Iniesta in the squad or in world soccer. That's the problem. We have great players in his position but there's no-one in the world like him," Luis Enrique told a news conference on Saturday.
"I try to control the number of minutes he plays but football is a contact sport and he's been injured a lot, he's had very bad luck in that respect."
Portugal international Andre Gomes is expected to fill in for Iniesta after his strong display after replacing him in the second half at Real Sociedad where Barca picked up a first win since 2007.
Barca have won all four of their fixtures with Eibar since the tiny Basque club, who have the smallest stadium in La Liga and the second smallest budget, were promoted to the top flight for the first time in 2014.
"Eibar always make things difficult so you have to be precise with the ball," said Luis Enrique.
"I'm a bit worried about the state of the pitch given the forecast, but I hope it doesn't affect the spectacle."
(Reporting by Richard Martin; editing by Brian Homewood)
