Inter Milan's grip on the Serie A title tightened considerably on Sunday as closest rivals Roma were held to a 1-1 draw at Messina.
Roma were in command after Brazilian winger Mancini had broken the deadlock with a low drive six minutes before half time.
But a series of missed chances came back to haunt them when Christian Chivu conceded a penalty in the 89th minute by needlessly clattering into Arturo Di Napoli.
Alessandro Parisi tucked away the spot-kick before picking up a second yellow card and being sent off.
A draw left Roma in second place on 42 points, nine behind Inter at the halfway stage of the season.
Reigning champions Inter had opened up a 10-point gap on Saturday by winning 3-1 at Torino for their 12th consecutive league win - a new Serie A record.
Palermo are four points behind Roma in third place after defeating Udinese 2-0 in Sicily where goals from Andrea Caracciolo and Cristian Zaccardo secured a solid rather than spectacular victory.
Catania could concede fourth place later on Sunday following their 2-1 loss at improving Chievo.
Lazio will leapfrog the Sicilians into the final Champions league spot up for grabs if they win at home to Siena in Sunday's late match.
AC Milan, hit with an eight-point penalty for match-fixing, continued their ascent with an unconvincing but vital 3-1 home win over Reggina.
Milan surged ahead with goals from Andrea Pirlo and Clarence Seedorf before Rolando's Banchi's rasping 25-yard shot reopened the contest for the visiting Calabrians.
Reggina were enjoying their best spell of the match when Alberto Gilardino finished off a swift counter-attack with an angled shot to ease Milan's jitters.
Cristiano Doni scored twice as Atalanta thumped Livorno 5-1 in Bergamo, while a coolly-struck penalty by Honduran striker David Suazo secured a 1-0 win for Cagliari against bottom club Ascoli.
Sampdoria against Fiorentina ended in a goalless draw.
Empoli beat relegation-threatened Parma 2-0 on Saturday to stake their claim as outsiders for fourth place.