After a string of fine performances for the Azzurri, the Bianconeri official has hailed the impact the former AC Milan midfielder has made on his squad since arriving in Turin
The 33-year-old has played a leading role in the Azzurri's Euro 2012 campaign, racking up one goal and two assists so far, and was named man of the match in the team's 2-1 victory against Germany on Thursday.
Such performances have followed up a fine domestic season, where Pirlo helped Juve to their first Scudetto since 2002-03, and Marotta hailed the impact the midfielder has made.
"Pirlo has been amazing, I think he is the best signing of my career," he told Rai Sport. "The circumstances were favourable for us to land him, just like when Sampdoria signed Antonio Cassano.
"An improved contract? He is a great professional, so that is just trivial. The most important thing is that he continues to make the difference.
"How much he is worth? Players like him are priceless.
Italy and Spain will face off in the Euro 2012 final on Sunday at 20:45CET.