The former Italy striker believes the midfielder gives Antonio Conte's side an edge whilst he does not see Didier Drogba as the answer to the club's striking problems upfrontAndrea Pirlo to be Juventus' key player as the Serie A champions take on another of the Italian's former sides Chelsea on Tuesday.
The midfielder has been imperious for Antonio Conte's team since moving to Turin from AC Milan in 2011, and Vialli believes La Vecchia Signora almost have an extra man when Pirlo is in the side.
"Juventus play like they have 12 men with him [Pirlo]. He is the director, the playmaker," he explained to Tuttosport.
He also admitted that Chelsea boss Roberto Di Matteo is likely to employ Oscar to try and combat Pirlo's passing game after the Brazilian scored twice in the reverse fixture at Stamford Bridge on matchday one.
He added: "Di Matteo will repeat the move, because it has brought great results. Oscar is the ideal player to put him in trouble, because he has the humility and the age to shoulder the dirty work and the quality in attack in turn.
"If Pirlo screens the defence, the Brazil international will allow him to take the ball and then attack him. We'll see what the outcome is."
Despite an impressive start to the defence of their Serie A title, Conte's team have been criticised for not having a regular goalscorer to spearhead their attack.
The Bianconeri coach has tried and tested two or three different partnerships with Mirko Vucinic, Sebastian Giovinco, Fabio Quagliarella, Alessandro Matri and on-loan Nicklas Bendtner to choose from, but has yet to settle on a pair he is happy with.
And Vialli was unsure as to who the best partnership would be to grab the goals to beat the European champions.
"The problem of the attackers of Juventus is that they are all the same level. No one has proven to be a champion and this explains the rotations of Conte," he continued.
"Overall, the team can benefit, but the individual certainly not. To answer that, I find it hard to choose a partnership. You can think of so many different combinations, but not one can be considered the strongest."
Former Blues' striker Didier Drogba has been linked with filling the void at Juventus Stadium, but Vialli thinks that the Cote d'Ivoire striker would not be the long-term answer to the issues that the club faces.
He added: "To win back the championship Juventus do not need Drogba. It would certainly not be a long-term investment and soon the problem would return again.
"It would be better to buy once and lock down the role for the next five years."