 In 2005, he was noticed by the dense network of observers of Juventus and signed, who decided to sell him in co-ownership to Siena, in which Juventus already had several players on loan.He made his debut in Serie A on 18 September 2005 in Siena - Palermo 1–2 and his first season in the top flight was characterised by ups and downs; losing the role of starting left-back to the more experienced Gianluca Falsini.For 2006–07, Juventus, relegated to Serie B by the 2006 Italian football scandal, allowed Molinaro to remain at Siena (who sold Falsini), relying on him to cover the role of left-back.