Frosinone completed a comeback from 2-0 down to win 3-2 at Cittadella, setting up a Serie B promotion play-off semi-final with Pordenone.
The other semi-final is between Spezia and Chievo, to be played over two legs between August 8 and 12.
Cittadella had surged into a 2-0 lead, Davide Diaw converting a penalty after just five minutes, then doubling his tally in first half stoppages on a classic counter, finished off with his volley.
However, deep into stoppages, Alessandro Salvi got Frosinone back into it when running on to a Nicolas Haas pass and skipping round his marker.
The visitors completed the comeback early in the second half, Salvi turning goal creator to set up Federico Dionisi for a spectacular right-foot curler.
Cittadella were unlucky to see Simone Branca’s left-foot rocket clip the upright, then he forced a stoppage-time save from Francesco Bardi.
The tie went into extra time, with a fingertip save on Andrija Novakovich of Frosinone, but in the very final minute, Camillo Ciano’s spectacular left-foot volley gave Alessandro Nesta’s club the 3-2 win.
Cittadella 2-3 Frosinone (aet)
Diaw pen 5, 46 (C), Salvi 49 (F), Dionisi 51 (F), Ciano 121 (F)