Inter Milan denied their neighbours AC Milan a place at the top of Serie A and threw their own hat into the ring for the Scudetto in the process with a 1-0 win at the San Siro.
A goal from Diego Milito in the 54th minute was enough to earn the visitors all three points and take them to within six points of the Serie A summit and just five of their city rivals.
Inter had a goal disallowed early on while Milan failed to make their territorial supremacy count as their attack proved too blunt.
Inter silenced the San Siro in the fifth minute, but Thiago Motta's celebrations after he nodded in a free-kick from the right were short-lived as he saw the linesman's flag raised.
The decision proved to be an incorrect one as the Italy international was not beyond the last Milan defender, although both Milito and Giampaolo Pazzini were stood in an offside position, perhaps contributing to the linesman's confusion.
It was only a rare venture into the Milan penalty area, though, as the Rossoneri kept hold of the reins to the game with Alexandre Pato wasting their first chance in the 11th minute when he lifted the ball over the crossbar from close to the penalty spot.
For all of their possession, Milan were unable to create any real openings and the next best chance of the game fell to Ricardo Alvarez, who found himself alone in front of Christian Abbiati, but he shot straight at the Milan goalkeeper in the 40th minute.
In the very last minute of the first half, Mark van Bommel rattled the crossbar with a shot from outside the area and Julio Cesar had to stretch to push Urby Emanuelson's shot wide on the rebound.
Inter started the second half like the first and opened the scoring in the 54th minute thanks, in part, to a mistake by Ignacio Abate.
He made a hash of his attempt to cut out a crossfield pass, allowing Milito to take the ball into the penalty area and beat Abbiati with a shot which went in off the base of the far post.
Inter's confidence levels rose and Yuti Nagatomo tested Abbiati shortly afterwards as the Nerazzurri threatened a second.
A reaction from Milan was inevitable, but it lacked any discipline as they rushed the ball into the Inter half, frequently losing possession and rarely threatening Julio Cesar's goal.
Coach Massimiliano Allegri brought on both Robinho and Stephan El Shaarawy but they failed to add any weight to the attack and Inter held on to their win without too much effort.