Real Madrid wing-back Marcelo lost his rag in the mixed zone after Saturday's home humiliation by Barcelona.
Marcelo was willing to answer questions after the 4-0 rout, but took unkindly to one reporter from Radio Marca.
Sport says the journalist asked if the problem on the night was Real's "attitude".
Marcelo snapped back: "Have you played football? Have you EVER played once at the Bernabeu?!,p> "You're not the best person to ask about attitude!
"YOU ARE STUPID!"
Marcelo, however, realised he was out of order and soon apologised to the reporter - who accepted the apology.