"We know the importance of Luis. What he gives you is invaluable, non-negotiable," Luis Enrique said at a news conference.
"If he then finishes in the area, that's great. He's essential and irreplaceable."
Barcelona struggled to find their best form in the opening 45 minutes, but improved after the break.
"We tried to fix the problems we had in the first half. With a team like Eibar, unbeaten away from home, it’s normal that we had trouble to get going," Luis Enrique added.
"Fortunately, we won the game with intensity and effectiveness in the final stretch.
"Going out there with three defenders isn't a problem as long as we are successful, but it isn't an exact science. It's about working hard and doing it better."
Barca are level on points with league leaders and rivals Real Madrid, who are unbeaten.