The hosts came within inches of breaking the deadlock after just eight minutes when Charles unleashed a first-time effort from just outside the box that crashed against the post.
They were left cursing their luck again five minutes later as Nolito rose highest inside the area to nod a cross off the very same upright.
Andreu Fontas was the next to threaten for Celta, doing so just after the half-hour mark as he nodded a cross narrowly over the bar.
The visitors almost broke the deadlock themselves with just under 10 minutes left of the half as Daniel Larsson latched on to a cross, controlling the ball in the area before drilling an effort towards goal that Yoel Rodriguez had to save.
Celta took the lead just two minutes later, however, as Fabian Orellana slid the ball through for Nolito to coolly finish in the bottom corner.
It was 2-0 a little more than a minute later as Orellana again acted as the creator, threading a pass between the defence for Charles to stab past the onrushing keeper.