AC Milan missed the chance to go sixth in the Serie A table after neither side managed to make the breakthrough in a hectic goalless draw at Sampdoria .
Massimiliano Allegri's men were eager to leapfrog Roma, who lost at Catania, but found themselves largely under the cosh in Genoa as Samp looked to claim their second big scalp in a week.
Lorenzo De Silvestri, Andrea Poli and Mauro Icardi whipped the Marassi faithful into a frenzy with a host of exciting plays, with Bojan Krkic and Kevin-Prince Boateng coming close for the visitors, but ultimately it was Delio Rossi's Blucerchiati who were left the more frustrated side.
Samp started well and steadily improved through a frantic first half.
De Silvestri tested Christian Abbiati's reflexes with a treacherous low drive inside five minutes, with the Milan goalkeeper then launching himself skyward to flick Poli's curling shot out of the far corner.
Eder was next to draw Abbiati across his goalmouth with a swerving drive after Kevin Constant conceded a free-kick.
Icardi, fresh from his brace at Juventus, nearly got on the end of a cross from deep on the left wing, but Philippe Mexes proved an unwelcome distraction.
In the 21st minute Samp enjoyed another fine chance, Daniele Gastaldello escaping the attentions of Milan captain Massimo Ambrosini to head just wide of the target.
Ambrosini's lapse in concentration was due to injury and the veteran midfielder was withdrawn for Mathieu Flamini.
Milan's forward line had been frozen out for 30 minutes but Bojan's near miss inspired a brief spell of dominance for the visitors.
Stephan El Shaarawy and Niang were being marked out of the game but midfielder Riccardo Montolivo did force a low save from Samp keeper Sergio Romero.
The Rossoneri prodded and probed but lost control when Bojan whipped a poor shot over the netting and into the Marassi crowd, with Eder's audacious backheel at the other end missing the mark before the half-time whistle.
Niang finally found space and time to make an impact as play resumed, weaving into the area to strike at goal with Romero barely tipping his effort out for a corner.
Samp tried to wrest back the initiative with a fine one-two between Icardi and Eder, which came to nothing, but the game would soon open up in spectacular fashion.
First, Niang wriggled free down the right, picking out Bojan who flicked the ball across the goalmouth for Boateng. The Ghanian found the target from an improbable angle but, remarkably, Romero's trailing hand was in the right place.
Samp then stormed down the other end to twice test Abbiati. Poli's initial strike did little to worry the Milan keeper but he closed his eyes as Icardi latched onto a loose ball only to slam it wide.
The fizz went out of the game as both defenses tightened up, substitute Fernando Tissone squeezing Flamini into a substandard attempt on goal with 10 minutes remaining.
Mexes closed down Eder's run before Boateng directed a horrible shot high and wide but, despite three minutes of stoppage time, there was no decisive moment at the Marassi.