The Tigre forward will attempt to fill the boots of the absent Ciro Immobile and Giacomo Raspadori, while Federico Chiesa has also withdrawn injured since Mancini made his initial selection.
With Gianluca Scamacca enduring a troubled first season at West Ham United, an in-form Retegui could make his Italy debut from the off at the tip of the attack in Naples.
Sassuolo's star man Domenico Berardi should get the nod on the right, while Freiburg's Vincenzo Grifo ought to fend off Lorenzo Pellegrini and Wilfried Gnonto for the final spot in the forward trident - assuming Mancini opts for a 4-3-3 setup.
Euro 2020 heroes Jorginho, Marco Verratti and Nicolo Barella are all fit and firing, so the trio could very well link arms in the engine room, although Sandro Tonali and Bryan Cristante are other options.
Giovanni Di Lorenzo and Leonardo Spinazzola can expect to bomb down the flanks as Mancini's full-backs, but Federico Dimarco has been forced to pull out and has been replaced by Emerson Palmieri.
Alessio Romagnoli and Francesco Acerbi can feel hopeful of forming a formidable centre-back partnership, with Inter Milan's Alessandro Bastoni also among the notable absentees this month.
Goalkeeper Ivan Provedel has also withdrawn - the uncapped Marco Carnesecchi has been called up instead - but Gianluigi Donnarumma remains his country's undisputed number one.
Italy possible starting lineup: Donnarumma; Di Lorenzo, Acerbi, Romagnoli, Spinazzola; Barella, Verratti, Jorginho; Berardi, Retegui, Grifo