Lazio edged 10-man Roma 2-1 at the Stadio Olimpico to climb to third in the Serie A table and sweep their rivals this season.
As hosts of this derby, Roma were almost immediately on the back foot after goalkeeper Maarten Stekelenburg was sent off for bringing down Lazio striker Miroslav Klose in the area.
Hernanes converted the resulting penalty in the 10th minute.
Roma equalised six minutes later through Fabio Borini but Stefano Mauri put Lazio in front for good shortly after the hour mark to send Roma to their first loss at home since October 23.
Lazio ended the game down to 10 men after Lionel Scaloni was sent off four minutes from time for a second bookable offence.
Lazio leapfrogged Udinese, who drew with Atalanta, into the last Champions League qualifying place. They are two points clear of Udinese.
The defeat left Roma 10 points behind Lazio.
Roma were without three regular starters - defender Marco Cassetti, midfielder Fernando Gago and striker Daniel Osvaldo - due to suspensions.
The home side suffered a major setback in the seventh minute when the referee handed Stekelenburg his marching orders after he pulled down Klose in the area.
Roma coach Luis Enrique had no choice but to bring in goalkeeper Bogdan Lobont in place of Erik Lamela.
Lobont stretched towards the left when Hernanes took the penalty but the attacking midfielder struck the spot-kick the other way to put Lazio ahead.
Roma responded by pushing forward and were rewarded.
Juan's diagonal effort hit the crossbar and his Roma team-mate Borini was first to the ball.
He shot from the heart of the area past Lazio goalkeeper Federico Marchetti to equalise.
Klose should have done better after the half-hour mark but his header from Francesco Matuzalem lacked power and proved an easy save for Lobont.
Before half-time, Alvaro Gonzalez's hard drive from 30 yards went over the bar.
Neither side could break through early in the second half and it was not until the hour mark that a chance was created.
Francesco Totti found space on the left and his right-footed shot from outside the area went inches wide of the far post.
One minute later and Lazio regained the lead when Mauri got behind Cristian Ledesma's free-kick and his left-footed strike from the heart of the area beat Lobont.
At the other end, Borini's right-footed volley went wide as Roma searched for the equaliser.
With 12 minutes remaining, Lobont kept out Mauri's goal-bound effort.
Roma could have clinched a point at the death but Borini headed substitute Marquinho's cross wide from a good position.
