The player's agent confirmed that discussions between the two clubs have begun and that a deal should go through.
Speaking to Radio Mana Mana Sport, Diego Tavano said: "The negotiations are taking place and the fee will be around 18million Euros.
"The attacker is well liked in Spain and he just needs to find the right emotional balance because he has incredible qualities."
Osvaldo has had his problems in Serie A over the last 12 months. Italy boss Cesare Prandelli dropped him for the Confederations Cup after he insulted club coach Aurelio Andreazzoli both on the field and via Twitter.