Champions Inter Milan opened up a three-point lead at the top of Serie A on Saturday with a thumping 5-0 win at hapless Genoa.
Inter's joy was further boosted by the 1-1 draw between title rivals Juventus and Fiorentina in Turin.
Sampdoria could still join Inter on 19 points at the scudetto summit if they win at Lazio on Sunday.
But this was a day when Jose Mourinho's Inter struck a significant blow in the title race, earning a crushing victory on one of the toughest grounds to visit and where they had already lost once this season to Sampdoria.
First half goals from Esteban Cambiasso, Mario Balotelli and a Dejan Stankovic stunner put the leaders out of sight before the break.
"I'd just say we won three important points. I'd swap this 5-0 for five 1-0 wins; we need points to win the title," said Mourinho.
"You can talk about individuals but I prefer talking about the team which gave us and our fans great joy."
Cambiasso's opener on six minutes had a touch of fortune about it.
As Maicon rose highest to meet Wesley Sneijder's free-kick, the ball dropped to Cambiasso whose weak shot towards goal was set to bounce harmlessly into Marco Aurelia's hands before Salvatore Bocchetti inadvertently diverted it in.
On 31 minutes Inter won back the ball in midfield and Sneijder quickly released Balotelli to shoot home first time from the edge of the box.
Inter were playing well but Genoa were not helping their cause and Amelia's fluffed punt upfield dropped to Stankovic out wide on the right and almost on the halfway line.
The Serbian then met the ball full on the volley to score from 50 yards with Amelia an embarrassed spectator.
Substitute Patrick Vieira added the fourth and Maicon wrapped up the victory as Inter continued to dominate after the break.
In rainy Turin, both Juventus and Fiorentina could have gone top, if only for a couple of hours, with a win but had to settle for a share of the spoils on a tricky pitch.
Juan Vargas opened the scoring for the visitors but Brazilian Amauri scored his first goal of the season for the hosts.
Worryingly for Juventus, this was their fourth Serie A game and fifth in all competitions in a row without a victory. They have won only one of their last seven matches.
"I'm not happy about this situation," said Juve boss Ciro Ferrara. "This point is not enough, we can't be satisfied with this result."
The visitors were far happier with the result following on from their recent 2-0 victory against Liverpool in the Champions League.
"We have to be satisfied with this performance on a difficult pitch," said Fiorentina coach Cesare Prandelli.
"The most important aspect is that last year we were happy with a point earned in Turin whereas now the lads are a bit down because they realise that they deserved something more."
Fiorentina were off to a flying start as playmaker Stevan Jovetic escaped the attentions of Fabio Cannavaro and Zdenek Grygera down the left and slipped in Vargas, who held off Christian Poulsen and beat Gianluigi Buffon at his near post after just five minutes.
But that only angered the hosts who soon came back with Vincenzo Iaquinta guilty of some profligate finishing, which eventually led to an equaliser on 19 minutes.
He shot straight at Viola goalkeeper Sebastien Frey from eight yards, before then poking wide from barely six yards out but his third miss was his worst and yet inadvertently set up Amauri.
Iaquinta completely hooked his shot on the turn well off target, but the ball ran across goal where the unmarked Amauri had the simple task of tapping into an empty net.