Surprise packages Napoli failed to take advantage of Milan's 0-0 draw with Lazio in midweek when they lost at Chievo but red-hot striker Edinson Cavani helped reduce Milan's lead to three points with a 2-0 win over lowly Cesena.
The Uruguayan, Serie A's top scorer with 18 goals, converted Christian Maggio's cross in the first half in Naples before Jose Sosa netted in stoppage time.
Champions Inter Milan surged up to third, five behind Milan with a game in hand, after Samuel Eto'o scored twice in an enthralling 5-3 home win over last season's runners-up AS Roma.
Wesley Sneijder struck early in his first start for over a month with a shot from the edge of the area, Roma's Simplicio soon equalised but Eto'o gave Inter the half-time lead following a breakaway.
Former Inter defender Nicolas Burdisso was sent off for conceding a penalty with a foul on Giampaolo Pazzini 17 minutes into the second period and Eto'o dispatched the spot-kick as last term's treble winners purred like never before in this campaign.
Brazil-born Thiago Motta celebrated his first call-up to the Italy squad with Inter's fourth before Mirko Vucinic and Simone Loria pulled goals back for Roma, who could soon have new American owners. Esteban Cambiasso bagged the hosts' fifth.
In Genoa, Milan took the lead when Alexandre Pato latched on to Zlatan Ibrahimovic's pass on 29 minutes only for home striker Antonio Floro Flores to strike in a loose ball.
LAZIO HELD
Milan's midfield was almost back to full strength after injuries and suspension but the hosts defended stoutly and deserved their point, with Rossoneri fans now fretting that a first scudetto since 2004 does not look as clearcut as before.
"We knew it wouldn't be easy against Genoa," Milan coach Massimiliano Allegri told Sky television.
"We were unlucky with their equaliser and in the second half we didn't play well, we gave away too many balls."
Fourth-placed Lazio missed the chance to pressure Milan themselves with a 1-1 home draw with Chievo.
Hernanes put the Romans in front with a ferocious free-kick deep into first-half stoppage-time but Cesar equalised.
Palermo lie just two points behind Lazio in fifth following a 4-2 win at struggling Lecce.
Previously struggling on-loan Juventus forward Amauri superbly netted his first Parma goal in a 1-1 draw with Fiorentina, who had Adrian Mutu back for the first time since being banished for quitting training last month.
Third-bottom Brescia won the relegation battle with basement side Bari, Alessandro Diamanti netting a penalty and Andrea Caracciolo an injury-time strike in a 2-0 victory.
Bologna beat Catania 1-0 to send the Sicilians closer to the drop zone with new coach Diego Simeone failing to stop a slide.
