FIFA rules state a player who is 28 and has played for the same club for five years can buy his freedom by paying the rest of his contract.
Ronaldinho has become frustrated at the Catalan club, who have held back for two years on a deal to extend his contract to 2014.
His brother Roberto De Assis admitted last night: "Contact with Milan or Chelsea?
"It is well known I have relationships with a lot of people and we talk about several different players.
"A player like my brother can attract the greatest clubs.
"Could he leave Barca? In football everything changes so quickly. He has an idyllic life at Barcelona but I can't say he will never leave."
If Chelsea owner Roman Abramovich does move to try to capture the Samba Boy, it would spark a huge battle for his signature.
However Europe's giants have a gentlemen's agreement not to poach players on the cheap by taking advantage of FIFA's rules.