( CNN ) -- Diego Milito scored the only goal as Inter beat Milan 1-0 in the San Siro derby , a result that threw open the Italian Serie A title race after the top three teams all failed to win on Sunday . After leaders Juventus and third-placed Udinese both struggled in earlier matches , defending champions Milan knew victory over their city rivals in the evening kick-off would send them two points clear at the top of the table . And Milan nearly took the lead on the stroke of halftime when Mark van Bommel 's strike crashed against the crossbar with goalkeeper Julio Cesar well beaten . Who are football 's top January transfer targets ? Inter made the most of that stroke of good fortune and Argentine forward Milito scored the only goal nine minutes after the break . Milan defender Ignazio Abate slipped as he attempted to clear Javier Zanetti 's cross and Milito was on hand to stroke the ball home . Inter 's victory consolidated fifth place , but just six points separate the top five teams after 18 games . The defeat left Milan a point behind Juventus , who remained top and unbeaten after a 1-1 draw at home to mid-table Cagliari . A superb team move resulted in striker Mirko Vucinic tapping home the opener for Juve after just seven minutes , but the Sardinian visitors leveled early in the second half through Andrea Cossu 's long-range strike . Udinese dropped two points behind Milan after slipping to a 3-2 defeat at Genoa . Damiano Ferronetti headed Udinese into the lead but quick-fire goals from Andreas Granqvist and Bosko Jankovic gave Genoa the advantage early in the second half . Rodrigo Palacio added a third before Antonio Di Natale pulled a goal back from the penalty spot after Genoa captain Marco Rossi had been sent off . Goals from Brazilian midfielder Hernanes and veteran Germany striker Miroslav Klose gave Lazio a 2-0 home win over Atalanta , putting the Rome club five points behind Juve in fourth position .
Leonardo Milito scores the only goal as Inter beat Milan 1 - 0 in the San Siro Stadium . The win opens up the Serie A title race with just six points between the top five . Juventus and Udinese fail to close but a close gap with 2 - 0 wins over Atalanta .