Serie A strugglers Siena somehow came away from a battering by Napoli with the advantage after the first leg of their Coppa Italia semi-final at the Stadio Artemio Franchi.
Visitors Napoli dominated proceedings but Siena, one place above the relegation zone in the league, took a two-goal lead through Reginaldo's and Gaetano D'Agostino's strikes either side of half-time.
Napoli finally got one back through an own goal from Emanuele Pesoli four minutes before the end, but it could have been better for the visitors with Hugo Campagnaro twice hitting the woodwork.
Edinson Cavani's early deflected shot was pushed wide by Simone Farelli, who then saved from Walter Gargano despite an awkward bounce.
Siena took the lead against the run of play three minutes before half-time.
Daniele Mannini hooked the ball on from the left flank, Reginaldo ran on to it and lifted a shot over the out-rushing Morgan De Sanctis and tapped home.
Former Napoli player Mannini should have extended the lead in the 54th minute when a weak defensive header reached him at the corner of the box, but his shot went over.
Ezequiel Lavezzi came off the Napoli bench in the 57th minute and almost made an immediate impact as his low, angled shot from the edge of the box went inches wide after a great pass by Camilo Zuniga.
Siena went 2-0 up after 66 minutes when, after a quick break down the left, captain Andrea Rossi sent in a low cross to D'Agostino, who finished low past De Sanctis.
Heading towards the final 10 minutes, Lavezzi cut in and his shot was pushed by Farelli towards Cavani, whose header was brilliantly nodded clear by Nicola Belmonte.
With six minutes to go, Napoli appealed for a penalty after what looked like a blatant handball from Matteo Contini, but no decision was forthcoming.
Campagnaro hit the right post from Lavezzi's free-kick, before Napoli finally caught a break when Pesoli slid in and diverted a low cross into his own net with Cavani lurking.
But there was still time for another moment of bad luck for Napoli when Campagnaro headed against the bar in the fifth minute of stoppage time.