Napoli's Serie A title ambitions took a huge hit in a 2-0 defeat at Champions League-chasing Inter on Saturday, while at the other end of the table Carpi gave their survival hopes a boost in a 4-1 win over 10-man Genoa.
Maurizio Sarri's Napoli were searching for a win that would have cut the lead of first-placed Juve to three points ahead of the reigning champions' encounter with Palermo on Sunday.
But, in the continued absence of suspended leading scorer Gonzalo Higuain, Napoli struggled to create chances.
And they were behind in the fourth minute when Inter's in-form captain Mauro Icardi excellently controlled Gary Medel's long ball and clinically finished past Pepe Reina, despite suspicions of offside, for his fourth goal in five games.
Icardi then turned provider for Marcelo Brozovic to make it 2-0 on the counter-attack shortly before the break, as Roberto Mancini's men closed to within three points of third-placed Roma, who face Atalanta on Sunday.
At Stadio Alberto Braglia, lowly Carpi pulled three points clear of the relegation zone after an action-packed encounter against Genoa.
Carpi fell behind after their defence switched off, believing Blerim Dzemaili was offside, but the midfielder was clearly on and did brilliantly to keep the ball in play before teeing up Leonardo Pavoletti to fire home.
But the match swung when Armando Izzo was harshly shown a second yellow card for a nudge on the counter-attacking Gaetano Letizia, and Carpi scored twice in first-half stoppage time to compound the visitors' misery.
The first was a wonderful overhead kick from Antonio Di Gaudio before Lorenzo Lollo poked home at the near post.
The additional four minutes earned the ire of Genoa coach Gian Piero Gasperini, who was sent off for his protests.
And there was no way back when Lorenzo Pasciuti made it 3-1 with a clever finish shortly after the restart and Stefano Sabelli added further gloss in the closing stages.
In Saturday's other Serie A contest, Torino leap-frogged Genoa into 10th as Andrea Belotti's 93rd-minute penalty sank Bologna in 1-0 victory.