CHIETI - Sampdoria substitute Mustacchio scored from 35 yards in the closing stages to give Sampdoria a 3-2 win over defending national champions Inter in the final of the Campionato Primavera - Trofeo Giacinto Facchetti.
Last season's beaten finalists made a strong start in Chieti and Eramo headed narrowly over before Bianco forced a punched save from Vid Belec.
Inter's first chance of the game fell to Mario Balotelli who tested Samp keeper Fiorillo from a free kick in the 18th minute.
Sampdoria had a goal disallowed in the 20th minute. Marilungo converted Bianco's right-wing cross but the referee blew for a foul by Sembrioni on Ivan Fatic.
Balotelli then struck a free kick into the sidenetting before Inter took the lead on 28 minutes. Gerbo played down the right wing to Ribas whose shot was blocked by Fiorillo. Daniele Pedrelli pounced on the loose ball and slotted past the keeper.
Samp levelled within four minutes through Poli, who shot into an open goal after Belec failed to hold Marilungo's shot.
Inter had more chances before the break, Balotelli and Siligardi forcing Fiorillo into saves.
The first chance of a slower second half fell to Fatic in the 50th minute, his free kick almost producing an own goal from Scappini.
Sampdoria edged in front in the 60th when Koman converted Scappini's headed assist from Marilungo's right-wing cross, but the Nerazzurri gave a quick reply, Balotelli scoring from the spot after Poli handled the ball in his area.
Second-half substitute Mustacchio sealed victory for the Blucerchiati with eight minutes remaining, his 35-yard effort taking a deflection off Federici, giving Belec no chance of making a save.
Inter 2-3 Sampdoria
Scorers: Pedrelli 28, Poli 32, Koman 60, Balotelli (pen) 64, Mustacchio 82.
Inter (4-3-3): Belec; Santon, D.Esposito, Federici, Fatic; Gerbo, Bolzoni, Pedrelli (Napoli 84); Balotelli, Ribas, Siligardi (Obi 65).
Subs not used: Tornaghi, Filippini, Caldirola, Destro, Khrin, Litteri.
Coach: Vincenzo Esposito.
Sampdoria (3-4-2-1): Fiorillo; Lanzoni, Rossigni, Sembroni; Eramo, Poli, Signori, Bianco; Koman (Mustacchio 68), Marilungo; Scappini (N.Ferrari 87).
Subs not used: Negretti, Fondaco, Calzolaio, Cucciniello, G.Ferrari.
Coach: Fulvio Pea.
Referee: Gambini (Rome).
Booked: Poli, Balotelli, Gerbo, Bolzoni.