Joaquin Correa scored twice for Lazio to dent AC Milan's Champions League hopes in a 3-0 defeat at the Olympic Stadium.
Argentina forward Correa struck after just 77 seconds and doubled Lazio's advantage early in the second half before Ciro Immobile added a late third.
Milan missed the chance to climb to second in the table and instead slipped to fifth, level on points with Napoli, who went third with a 2-0 win at Torino, and fourth-placed Juventus with five games remaining.
Second-placed Atalanta are two points better off, with the race for the Champions League places set to go down to the wire.
Lazio, in sixth, closed the gap to the top four to five points, plus they also have a game in hand on their rivals.
Napoli boosted their hopes of a top-four finish with a seventh win in nine league matches at relegation-threatened Torino.
Tiemoue Bakayoko and Victor Osimhen scored within two minutes of each other early in the first half to put Napoli in control.
Napoli pair Piotr Zielinski and Lorenzo Insigne both struck a post with shots in either half, while Torino's cause was not helped when Rolando Mandragora was sent off for his second yellow card in the closing stages.
Sweden forward Isak fired home midway through the first half to make it back-to-back wins for Sociedad, who stay in fifth place.
Bottom club Eibar remain seven points from safety after a fifth straight defeat.