Lazio denied AC Milan a chance to take top spot in Serie A by winning 2-0 on Wednesday night with late goals at the Stadio Olimpico.
Hernanes put Lazio ahead in the 76th minute before Tommaso Rocchi capped off a wonderful evening for the hosts with five minutes remaining.
The Rosssoneri controlled possession throughout but could not find a way past Lazio goalkeeper Federico Marchetti as they dropped valuable points in Rome in their battle for the Scudetto.
The result, Milan's fourth defeat of the season, has left them one point behind Serie A leaders Juventus, who have a game in hand after their scheduled match at Parma was postponed on Tuesday due to the snow that has hit Serie A this week.
Lazio, meanwhile, remain fourth, four points adrift of Milan.
The Biancoceleste went into the game looking to avenge their 3-1 loss at Milan last month that knocked them out of the Coppa Italia.
The visitors had the better of the opening stages and could have taken the lead in the sixth minute, when Antonio Nocerino got his head behind Zlatan Ibrahimovic's cross and his effort was kept out by Marchetti.
Midway through the first half, Cristian Ledesma made a crucial tackle with prevented Ibrahimovic from having a clear run on goal.
On the half-hour mark, Hernanes' 30-yard strike forced AC Milan goalkeeper Christian Abbiati to fully stretch to clear.
Before half-time, Ibrahimovic wasted a good chance when he opted to pass instead of taking a shot from close range.
Milan could have broken the deadlock early in the second half when Robinho fed Massimo Ambrosini in the box but his shot on the turn went inches wide.
Lazio responded with a 30-yard volley from Abdoulay Konko which Abbiati tipped over the bar on the hour mark.
The hosts went in front soon after when Rocchi fed Hernanes inside the box and his right-footed strike towards the left corner of goal beat Abbiati.
AC Milan coach Massimiliano Allegri then handed new signing Maxi Lopez his debut but Lazio doubled their lead soon after.
A fast counter-attack saw Senad Lulic get past his marker and find
Rocchi inside the area and the Italian forward struck the ball from 10 yards past Abbiati.
Lopez, who joined Milan from Catania this week, almost got on the scoresheet but his header from Ibrahimovic's cross was kept out by Marchetti.
