Champions League contenders Juventus remained on course for their 29th Serie A title despite a 1-1 draw with closest challengers Napoli and the continued resurgence of AC Milan.
Juventus will host Celtic on Wednesday in the second leg of their last 16 tie having romped to a 3-0 win over the Scottish champions in Glasgow.
However the champions were lucky to emerge with a share of the points on Friday after Napoli laid siege to Gianluigi Buffon's goal before the game ended 1-1.
Juve have a six-point lead over Napoli with Milan, who beat 10-man Lazio 3-0 on Saturday despite missing injured striker Mario Balotelli, in third a further five points off the pace.
"The title is far away, we are six points in front which is a good advantage," said Juve coach Antonio Conte.
"But there are another 33 available and we still have to play Milan, Inter and Catania. We must always be gritty, determined and motivated to get the points, because every match is difficult and a surprise is always around the corner."
Massimiliano Allegri, who led Milan to the title in his first season in charge in 2011 and a runner-up place last year, almost failed to make it past Christmas because of his side's woeful start to the season.
But Milan stunned Barcelona 2-0 in the first leg of their Champions League last 16 tie two weeks ago and are now well-placed to secure the final Champions League spot, although Inter are snapping at their heels.
A week after the Milan derby finished 1-1, Inter showed grit and determination to overcome a 2-0 deficit and stun Catania 3-2 on Sunday thanks to an injury-time winner from Rodrigo Palacio, who scored a brace.
Juve, Napoli, Milan, Inter and Lazio are all vying for the coveted European places having missed out on the Champions League this season.
Unsurprisingly, Inter coach Andrea Stramaccioni was a relieved man as his team jumped up to fourth to keep their fellow challengers within sight.
"We had a terrible 20 minute period and were punished for our mistake on the first goal," Stramaccioni told Sky Italia.
"Luckily this team has thick skin and managed to fight their way back into the game.
"It's an important victory for us against a team which is in great form. Thankfully the real Inter emerged after the interval."
Fiorentina beat Chievo 2-1 to sit 14 points behind Juventus but only three shy of third-placed Milan.
Bologna climbed further away from the relegation zone with a 3-0 home win over Cagliari while Sampdoria had Emanuel Icardi to thank for the 58th minute header which secured a 1-0 win over Parma.
At Siena, Giacomo Bonaventura scored a brace for Atalanta to secure a precious 2-0 away win.
There was some history-making in Sunday's late match when Roma captain Francesco Totti became the joint second all-time top scorer in Serie A with a 225th career goal during a 3-1 win over Genoa.
Totti, 36, stepped up to beat Sebastien Frey from the spot in the 16th minute after a controversial penalty award following Cesare Bovo's challenge on Mattia De Rossi.
Genoa levelled just before the break when Marco Borriello scored from the spot, only for 18-year-old Alessio Romagnoli to meet a corner and beat Frey shortly before the hour mark.
Slovakian midfielder Juraj Kucka was then shown a second yellow card for an altercation with Totti and sent off, with Simone Perrotta securing all three points on 88 minutes.
Totti now shares second place on 225 goals with Sweden's Gunnar Nordahl, formerly of AC Milan -- both of whom trail Silvio Piola by 49 goals.
"I really wanted this goal and to get it in front of our own fans is special," Totti told Sky Italia.