Unionistas president Roberto Pescador has fired a warning at Barcelona.
The minnows have drawn Barca in the Copa del Rey round of 16 after their giantkilling of Villarreal.
Pescador reacted to the pairing, stating: "For us it is a great prize, we are happy, it is one of the great teams in Spanish football and among the best in the world, but in our stadium everyone suffers.
"They're going to suffer too, that's for sure. There can't be more spectators than we saw against Villarreal because that's the maximum number of people we can accommodate."
However, Pescador heaped praise on the turf.
"We have been paying for it for two years, we had to change it to be able to continue competing in the Primera RFEF and it is spectacular. It's one of the best in the division."
And on the problem with floodlights, he reassured: "It was not at the stadium, but in an external electrical substation. It was something specific, it's been resolved, and it shouldn't happen again."