The Partenopei missed a host of chances at the Artemio Franchi and, after twice being caught out on the break, they were grateful to a late own goal for keeping them right in tie
Two goals in either half from Reginaldo and Gaetano D'Agostino gave Siena a 2-1 first-leg lead in the Coppa Italia semi-final on Thursday night against Napoli.
A late Emanuele Pesoli own goal gave Napoli some hope, but the two earlier breakaway goals from Giuseppe Sannino's side were enough to give them a one-goal lead going into next month's second leg.
With Siena playing in their first ever Coppa Italia semi-final, it was no surprise that, with a number of key players missing, they started rather tentatively; Reginaldo fluffing a number of passes in the final third within the first few minutes.
And it wasn't long before Napoli very nearly made them pay for their sloppy start. Marek Hamsik released Edison Cavani inside the area, and the Uruguayan struck a first-time effort towards Gianluca Pegolo's near post, only for the 'keeper to tip it away for a corner.
The Bianconeri soon awoke from their haze, and it was D'Agostino who went closest to opening the scoring for the Tuscans on 15 minutes. A superb turn and shot from 25 yards out whistled past Morgan De Sanctis, but also just past the goalkeeper's left-hand post.
Goran Pandev had a fine effort saved midway through the half, but on 42 minutes Reginaldo opened the scoring quite unexpectedly for Sannino's side. The Brazilian racing through onto a terrific pass from Daniele Mannini, cheekily flicking the ball over the on-rushing De Sanctis, and slotting easily into an empty net to make it 1-0 to the hosts' at half time.
The teams returned for the second half, and with Napoli a goal behind and with the bit between their teeth, it was Cavani who had the best chance of the opening exchanges.
A cross from Hamsik on the left-hand side of the area found the former Palermo man unmarked on the penalty spot, but his header was straight at Pegolo, and the 'keeper managed to gather the ball with ease.
Two quick-fire efforts from Mannini forced De Sanctis into a pair of impressive saves, but it was at the other end where the next goal was looking most likely to come from.
A low cross from the left by Juan Zuniga found the substitute Ezequiel Lavezzi on the edge of the area, and the Argentine forward fired in a first-time effort that flew just inches wide of the right-hand post.
Walter Mazzarri's side soon came to regret those missed chances, though, on 65 minutes. A wonderful counter-attacking move culminated in Andrea Rossi, on the left-hand side of the box, laying the ball across goal for D'Agostino to tap in from six yards.
The Partenopei would not be beaten though, and a cross from Lavezzi five minutes from time, hit the out-stretched leg of Pesoli, with the former Varese defender guiding the ball into the back of his own net.
Despite some more late Napoli attacks, Mazzarri's side couldn't quite get the equaliser, and go into the second leg at the San Paolo in six weeks' time 2-1 down.