Barcelona were furious with referee Mario Melero Lopez in the final moments of their defeat on Sunday, Pique in particular confronting the official.
From the 88th minute on, the visitors picked up five yellow cards as they argued with decisions, such as the one in which Yerry Mina was deemed to have fouled goalkeeper Oier Olazabal.
"Be careful, don't touch me," said Melero as Pique protested the call, witnessed by El Dia del Futbol. "Don't threaten me, don't threaten me."
However the defender was left apoplectic and spoke back to the referee, which was later put on record in Melero's post-match report.
"Don't threaten you? You are threatening me," he exclaimed.