Gonzalo Higuain fired Napoli to the summit of Serie A as they won the top-of-the-table clash with Inter Milan 2-1.
The Argentina frontman struck the opener after just 65 seconds and added the second after the break to send the hosts a point clear of their opponents in second.
Inter had to play the second half with 10 men after defender Yuto Nagatomo was sent off moments before the interval.
And although they pulled one back through Adem Ljajic, Napoli held on to give their title hopes a major boost.
The visitors had kept a clean sheet in their previous four matches but their rearguard was breached with Napoli's very first attack.
Jose Callejon brought down a poor clearance on the edge of the area and Higuain took the ball in his stride before smashing home a superb angled shot on the turn with his right foot.
Inter's hopes of getting back into the match suffered a blow on the stroke of half-time when Nagatomo, already on a booking, needlessly clattered Napoli midfielder Allan on the touchline to earn a second yellow card.
Higuain grabbed his second just after the hour mark when he latched onto Raul Albiol's headed clearance, burst between two defenders and clipped home his 14th goal of the season.
The 10 men halved the deficit in the 67th minute when Ljajic capitalised on some hesitant defending to beat Napoli keeper Pepe Reina at his near post.
And twice they could have snatched a point in stoppage time only to be denied by the woodwork, with Stevan Jovetic hitting one post and Reina dramatically pushing Miranda's header onto the other.
Fiorentina could have gone top, albeit for a couple of hours, had they beaten Sassuolo in the early kick-off.
But the surprise package this season could only manage a 1-1 draw after Sergio Floccari cancelled out Borja Valero's opener.
In the fifth minute Josip Ilicic's low cross was missed by Giuseppe Rossi but Valero dug the ball out from under his feet to fire home from eight yards.
But four minutes before the break Sassuolo hauled themselves level when Floccari towered above three defenders to nod Sime Vrsaljko's floated cross past Fiorentina keeper Ciprian Tatarusanu.