AC Milan beat Inter 1-0 at the San Siro on Sunday to cut their city rivals' lead at the top of Serie A to seven points.
Ecuador full-back Pervis Estupinan scored the decisive goal in the first half for Milan, who have 60 points from 28 games, with 10 matches to go.
Champions Napoli, who beat Torino 2-1 at home on Friday, are four points further back in third.
Como won 2-1 at Cagliari on Saturday and have climbed to fourth place, which is good for Italy's last slot to qualify for next season's Champions League.
They have 51 points and are ahead of fifth-placed AS Roma, who lost 2-1 at Genoa on Sunday, on goal difference.
Juventus are sixth with 50 points after thumping promoted Pisa 4-0 in Turin.
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