Irishman O'Shea delayed naming his replacements for Italy's second test in their November series until Thursday.
Fresh from a 68-10 defeat to New Zealand, Irishman O'Shea delayed naming his replacements for Italy's second test in their November series until the end of training on Thursday.
Treviso's Ornel Gega has already replaced injured hooker Leonardo Ghiraldini at hooker while Sami Panico has come in for injured prop Andrea Lovotti, after O'Shea named his starting XV earlier in the week.
Quaglio has earned his first call-up to the squad while Ferrari was part of Italy's June tour of the Americas but was unused by O'Shea, who signed a four-year deal after replacing Jacques Brunel in the summer.
Also among the replacements is Zebre centre Tommaso Boni, who came off the bench to score Italy's only try last week at Rome's Stadio Olimpico, club-mates Tommaso D'Apice and George Fabio Biagi and Treviso trio Edoardo Gori, Tommaso Allan and Abraham Steyn.
Italy have played South Africa 12 times and lost on each occasion, although the Azzurri will be looking to pounce on a Springboks team currently enduring a wretched run.
They have now conceded five defeats in their last six tests, including a first defeat to England in a decade last week at Twickenham.
Earlier in the week O'Shea recalled Giovanbattista Venditti to replace Angelo Esposito on the left wing while Francesco Minto comes off the bench to replace Maxime Mbanda in the back row.
"I'm looking forward to playing South Africa next week. For me, the glass is always half-full," said O'Shea.
Italy team to play South Africa at the Stadio Artemio Franchi in Florence on Saturday (kick-off: 1400 GMT):
Edoardo Padovani; Giulio Bisegni, Tommaso Benvenuti, Luke McLean, Giovanbattista Venditti, Carlo Canna, Giorgio Bronzini; Sergio Parisse (capt.), Simone Favaro, Francesco Minto; Andries Van Schalkwyk, Marco Fuser; Lorenzo Cittadini, Ornel Gega, Sami Panico
Replacements: Tommaso D'Apice, Nicola Quaglio, Simone Ferrari, George Fabio Biagi, Abraham Steyn, Edoardo Gori, Tommaso Allan, Tommaso Boni