Second-placed Napoli dominated the second-half but left San Siro frustrated after failing to break down AC Milan in an 0-0 Serie A draw on Saturday.
Napoli should have snatched a win when they had four men against two on the break late in the game but they took one pass too many and the move ended with Piotr Zielinski's shot saved by Gianluigi Donnarumma.
Zielinski had two other efforts saved by the 19-year-old goalkeeper and the Polish midfielder also rifled another effort centimetres past the foot of the post.
Napoli, with 48 points, closed the gap on leaders Juventus to eight points, ahead of the Turin side's visit to Lazio on Sunday, while Milan are fourth with 35 points.
Napoli ended with 10 men after Fabian Ruiz was given a second yellow card for handball in stoppage time although the ball appeared to hit his chest.
Shortly afterwards, Napoli coach Carlo Ancelotti was ordered from the touchline for dissent.
Milan had two good chances in the second half but Franck Kessie's effort from six metres was deflected over the crossbar and Napoli goalkeeper David Ospina denied Mateo Musacchio with a brilliant reflex save on the line.