AC Milan avoided an embarrassing home defeat and damaged Frosinone's survival hopes in a dramatic 3-3 draw at San Siro while Miroslav Klose and Antonio Candreva gave Lazio a 2-0 win over Inter, which ended Roberto Mancini's hopes of securing a UEFA Champions League spot.
Despite his AC Milan team mounting a comeback from 2-0 down, Cristian Brocchi has still tasted victory only once since taking charge of the 18-time Italian champions, who are six points outside the UEFA Europa League qualification places with only two matches of the Serie A season remaining.
Visiting Frosinone scored twice in the first half, through Luca Paganini and Oliver Kragl, but also relied heavily on the excellence of goalkeeper Francesco Bardi.
He saved a Mario Balotelli penalty, and, though Carlos Bacca soon pulled a goal back early in the second half, Federico Dionisi restored the advantage.
But Luca Antonelli made a fight of it again for Milan, and Jeremy Menez prospered where Balotelli had not to equalise with a late spot-kick.
The result left Frosinone second from bottom, four points from safety, while Milan may have to beat Juventus in the final of the Coppa Italia if they are to earn a route into European competition.
Inter's top three hopes came to an end as they were comfortably beaten by Lazio.
Mancini's side needed a victory to keep their top-three chase alive, but Klose's early goal gave them a deficit they never looked likely to claw back at the Stadio Olimpico.
Candreva converted a late penalty to secure the win after Jeison Murillo had been sent off, ensuring three points for Lazio and guaranteeing that Serie A's Champions League spots will go to champions Juventus, Napoli and Roma.
Palermo gave their own relegation battle a huge boost as they beat Sampdoria 2-0 to move level on points with 17th-placed Carpi, thanks to Franco Vazquez's first-half strike and an own goal from Nenad Krsticic just five minutes from time.
Sassuolo, meanwhile, remain sixth - a point clear of Milan - thanks to Lorenzo Pellegrini's solitary strike against already-relegated Hellas Verona.