Goals from Diego Milito and Goran Pandev gave Inter Milan a 2-0 win over city rival AC Milan on Sunday, extending its lead at the top of the Serie A to nine points.
Inter played most of the match with 10 men after midfielder Wesley Sneijder was sent off for sarcastically applauding referee Gianluca Rocchi and it finished with only nine on the pitch after Lucio was also red carded for a deliberate handball in second half stoppage time.
"Everything was good," Inter coach Jose Mourinho said. "After a few minutes it was clear it was the type of match in which you could see that Inter was in control, concentrated and ready for the task. Inter was excellent and even with 10 men we were even better."
The result means Inter remains top with 49 points. Milan is second on 40, though Leonardo's side does have a match in hand.
Inter made the better start, with Sneijder twice going close. He hit the outside of the post with a long range shot and then forced Milan goalkeeper Dida into a sharp save from close range.
Milito opened the scoring in the 10th minute after his strike partner Pandev found him in space behind Milan's defense and the Argentine shot low under Dida.
Inter went down to 10 men in the 27th minute when Sneijder was dismissed. Until then, the Dutchman had been dominating the midfield and his teammates had to lead him away from referee Rocchi and off the pitch.
"Is it right that a player gets sent off for clapping his hands, but not when a player runs halfway across the pitch in an aggressive manner," Mourinho said.
Milan began the second half more brightly and Inter keeper Julio Cesar had to be alert to stop Clarence Seedorf's close range header, while Ronaldinho went close moments later with a shot from the edge of the area.
Milan's Marco Borriello then twice headed on target as David Beckham began to find more space to cross from the right wing.
However, it was Inter that added to the scoreline, Pandev curling home a freekick in the 65th minute after Giuseppe Favalli brought down Maicon.
Cesar stopped Milan from adding a consolation goal in injury time, when he saved Ronaldinho's penalty after Lucio had been sent off.
"Inter had a great game and were good in defense and controlled the play well, even with 10 men," Leonardo said. "They didn't change much with 10 men. They just pulled Pandev back and did their best to win the ball.
"We created a lot of chances at the start of the second half, but couldn't quite find the goal," Leonardo added. "There is much of the season left to play and I am happy with how we are doing, even if we lost the derby."
In Sunday's earlier games, Abel Hernandez scored twice and Igor Budan once to help Palermo to a 3-0 win over Fiorentina that took the Sicilian side up to fifth.
Palermo has 34 points, three behind Napoli in fourth place. Napoli beat Livorno 2-0, with Cristian Maggio scoring in the first half and Luca Cigarini adding a freekick in second-half injury time after Livorno goalkeeper Alfonso De Lucia was sent off for a deliberate handball.
Juventus, which lost 2-1 at home to AS Roma on Saturday has now slipped to sixth place following five losses in six matches.
Palermo took the lead in the 28th minute. Fabio Miccoli shot from the edge of the area and hit the bar but Hernandez reacted fastest and headed into the open goal.
The Uruguayan doubled his tally in the 37th, running through to steer the ball between goalkeeper Sebastien Frey's legs after Juan Pastore had slipped a pass through the Fiorentina defense.
Budan added the third in the 57th minute when Fabio Liverani flicked on Miccoli's freekick and the Croatian spun round and volleyed past Frey.
"I am very happy with the match," Palermo coach Delio Rossi said. "We wanted a good showing and I am happy for the guys.
"The Champions League is still a far off dream, but we shall see," Rossi said. "I haven't done much, the praise should go to the players who believe in what we are doing."
Napoli went on to win its game after Livorno striker Cristiano Lucarelli squandered a great chance to open the scoring in the 29th minute, heading over from close range, and then missed a penalty in the second half.
"I am very proud of what these players did," Napoli coach Walter Mazzarri said. "Today we had a lot of players missing and it was an important test for us.
Shortly before the break, Napoli had a strike by German Denis ruled out as the Argentine was offside, but Maggio made no mistake in first half injury time. Cigarini hit a long pass from the back and Maggio volleyed home his fourth goal of the season.
Nine minutes into the second half, Michele Pazienza fouled Livorno's Martin Bergvold in the area, but Napoli goalkeeper Morgan De Sanctis saved Lucarelli's penalty and the striker hit the rebound wide.
"We are still a bit naive and nearly threw away the result," Mazzarri said. "We were missing a few players and our resources were stretched, but we stuck to our job and that bodes well for the future."
In the closing minutes, De Lucia was dismissed for his handball on the edge of the area. Midfielder Davide Marchini went in goal, and could do little to stop Cigarini scoring with a freekick.
Also Sunday it was: Bologna 2, Bari 1; Genoa 2, Atalanta 0; Lazio 1, Chievo Verona 1; Siena 1, Cagliari 1; and Udinese 2, Sampdoria 3.