AC Milan were held 1-1 at home by Lazio as they missed the chance to go one point behind Inter, while Juventus bounced back with victory over Atalanta and Fiorentina beat Udinese.
Milan were looking to put pressure on leaders Inter after their arch-rivals lost to Roma on Saturday, but they could not take advantage of the Nerazzurri's slip-up.
The home side got off to a good start at the San Siro when striker Marco Borriello put the Rossoneri in front from the penalty spot after 19 minutes.
However, Leonardo's men were pegged back just after the half-hour mark when Stephan Lichtsteiner equalised, and Lazio held on for a point.
Udinese are still four points clear of the relegation zone at the wrong of the table, but the result leaves them looking over their shoulder once more.
The Viola took the lead after 36 minutes through Juan Manuel Vargas, but Simone Pepe equalised for the away side just four minutes later.
Things went downhill for the Bianconeri after the break, however, as goals from Alberto Gilardino, Mario Santana and Stevan Jovetic sealed the win.
Juventus moved closer to the UEFA Champions League places with a 2-1 win over Atalanta, although they left it late to secure the three points.
After a turbulent period for the Turin-based club, Alberto Zaccheroni's side showed their character right until the final whistle.
Alessandro Del Piero opened the scoring on the half-hour mark but Juve were pegged back on the stroke of half-time thanks to an effort from Nicola Amoruso.
Substitute Felipe Melo netted the winner with eight minutes remaining to move the Old Lady up to sixth, while Atalanta remain in the drop zone.
Fellow European hopefuls Napoli also picked up a victory and stay above Juve on goal difference.
Defender Paulo Cannavaro scored the only goal of the game five minutes after the break against Catania, who do not advance from 14th position.
Sampdoria, though, drop to seventh following a disappointing 1-1 draw at home to Cagliari.
Stefano Guberti had opened the scoring for Samp on 48 minutes and they looked on course for an important win.
But substitute Nene equalised on 80 minutes and the game ended in a stalemate, although Nene was then sent off deep into injury-time.
Another 1-1 draw saw rock-bottom Livorno hold Bari at Stadio Armando Picchi.
Despite an 85th minute equaliser from Francesco Tavano, Livorno are still seven points adrift of safety and seem doomed to relegation this term.
Bari took the lead in the first half through Riccardo Allegretti, but drop to 10th with dreams of Europe beginning to fade.
Genoa are one place above Bari but they could only muster a 0-0 draw away at second-from-bottom Siena.
Meanwhile, Parma and Chievo played out a goalless stalemate at Marc' Antonio Bentegodi, as both sides seem destined for a mid-table finish.