Chelsea owner Roman Abramovich is on red-alert to swoop for the frontman with a £50 million bid after meeting with De Assis last month.
Ronaldinho, 27, is furious he was fronted up by Rijkaard over allegations of boozing less than 48 hours before a game.
Rijkaard said: "The player told me it was not true. I believe him."
But De Assis rapped: "I'm sure a campaign exists against Ronaldinho. I have read many absurd stories about his nightlife."