AC Milan had Mattia De Sciglio sent off inside a minute as they slipped to a 3-0 defeat at Napoli, who moved to within four points of third-placed Lazio.
De Sciglio saw red just 45 seconds into the contest, but it took Napoli 70 minutes to make their extra man count, with Marek Hamsik putting them in front.
Gonzalo Higuain and Manolo Gabbiadini added two more in quick succession to seal the points for Rafael Benitez's men and leave Filippo Inzaghi's Milan all but mathematically out of the running for a place in Europe next season.
The match had barely started when De Sciglio tripped Hamsik inside the area, conceding a penalty and earning one of the quickest red cards on record.
A further two minutes passed before Higuain was finally able to take the spot-kick, but Diego Lopez dived the right way to turn his effort behind.
It was nevertheless a major ask for the Rossoneri to hold on with 10 men for the remainder of the game, even if they resisted well and even went closest to scoring in the first half with Giacomo Bonaventura's header grazing the outside of a post.
Napoli flew out of the blocks at the start of the second half, with Jose Callejon's shot blocked just 30 seconds in.
A Hamsik effort was turned against a post by Gabriel Paletta, with Benitez beginning to lose his patience on the touchline, along with many of the fans inside the Stadio San Paolo.
Napoli finely broke through with 20 minutes remaining, a finely-placed shot from Hamsik hitting the base of the right-hand post on its way past Lopez.
With Milan's resistance now broken, it was not long before goal number two arrived. Higuain doubled Napoli's lead five minutes later, tucking the ball in after Gabbiadini intelligently left Dries Mertens' pass to the Argentinian.
Gabbiadini showed even greater intelligence and incredibly quick thinking as he added a third two minutes later, turning the ball in from behind him with his heel after it ricocheted back off Lopez.
Those three goals in six minutes were enough to complete the job as Napoli threw their hat back into the ring for a top-three finish and a place in the Champions League next season.