Lazio beat Inter Milan 1-0 with a superb Miroslav Klose volley to give to give Edoardo Reja a winning start to his second stint as their coach and third-placed Napoli beat Sampdoria 2-0 thanks to a brace from Dries Mertens.
Hellas Verona won 3-1 at Udinese helped by two goals from Luca Toni, the first courtesy of a blunder from home goalkeeper Zeljko Brkic who allowed an apparently harmless shot to slip between his legs in the eighth minute.
The win took the promoted side into fifth place, above Inter.
Parma defender Alessandro Lucarelli scored with a cheeky backheel following a corner as Roberto Donadoni's team came from behind to beat Torino 3-1 and striker Amauri scored his first goal of the season to complete the scoreline.
Bottom club Catania beat Bologna 2-0 in a relegation scrap and improving Genoa overcame lowly Sassuolo by the same score.
Napoli's win lifted them to 39 points from 18 games, two behind Roma who lost 3-0 at leaders Juventus on Sunday. Juventus have 49 points, a massive eight clear at the top.
Monday's games were played amid concern about Serie A leading goalscorer Giuseppe Rossi after he suffered a third injury to his troubled right knee in Fiorentina's 1-0 win over Livorno on Sunday.
Fourth-placed Fiorentina said that Rossi had sustained a second degree sprain to the medial collateral ligament.
Although worrying, there was relief that he avoided damage to the anterior cruciate ligament, which has been operated on twice and cost him two years of his career.
Milan, whose coach Massimiliano Allegri confirmed over the Christmas break that he would step aside at the end of the season, climbed to a modest 11th on 22 points.
Former World Player of the Year Kaka, who returned for a second stint at Milan at the start of the season, put them in front 10 minutes before the break with his 100th goal for the club in all competitions.
The Brazilian swept home Urby Emanuelson's cross from a tight angle after Milan broke following an Atalanta corner.
Yohan Benalouane had a goal disallowed for Atalanta and German Denis was denied by Christian Abbiati as Milan showed signs of faltering before Kaka struck again, firing home after Robinho scuffed Mario Balotelli's cross in the 65th minute.
Two minutes later, Cristante celebrated his first Serie A start by scoring a pinpoint 25-metre shot which went in off the foot of the post.
"Kaka played excellent football working for the team and scoring twice," Allegri told reporters. "I'm very happy for him and the objective that he's reached.
"We all need to be focused on ending the season in the best way that we can and aware that we still have a long way yet to go."
Reja, who resigned as Lazio coach 18 months ago, was brought back in a rush after the club sacked Vladimir Petkovic following his announcement that he would be taking over as Switzerland coach next season.
Lazio president Claudio Lotito was angry at the move even though Petkovic's contract ended in June before he starts his new job.
A scrappy game appeared set to end in stalemate until Antonio Candreva sent over a cross from the right and Germany forward Klose got in front of his marker to score with a majestic volley from 12 metres.
Mertens provided the breakthrough for Napoli when he volleyed in Gonzalo Higuain's cross in the 53rd minute and the Belgian curled in a 25-metre free kick nine minutes later.
Image: Kaka of AC Milan celebrates scoring his 100th goal for the club
Photograph: Claudio Villa/Getty Images
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