If it is confirmed that both Melo and Marchisio out, not to mention Tiaga, we must play 4-2-3-1. There is no point in playing out of form players, or players who are not 100% fit.
Poulsen doesn't deserve to, and should not start, and Marrone is too inexperienced at this level. I doubt Sissoko has 90 minutes in him, and a midfield trio of Poulsen, Camo, and DC just scares me. It looks too imbalanced, and will get totally owned by Fiorentina.