Simone Inzaghi's side are provisionally ahead of Napoli after netting all five of their goals in the opening 45 minutes at the Stadio Bentegodi through a Marcus Thuram brace and further strikes from Joaquin Correa, Stefan de Vrij and Yann Bisseck.
Napoli coach Antonio Conte criticised the Video Assistant Referee (VAR) for not intervening to reverse a penalty that Inter Milan's Hakan Calhanoglu eventually missed in their 1-1 draw on Sunday.
The Italian champions remain undefeated in the competition this season and sit fifth on 10 points at the midway point of the new league phase format.
Inter are now in second place in the table with 24 points, one behind leaders Napoli, while Venezia are 18th.
Manager Thiago Motta acknowledged that Juventus are not in the Serie A title race just yet and emphasised the importance of maintaining focus on their growth after they secured a dramatic 4-4 draw with champions Inter Milan thanks to two late goals on Sunday.
Argentina striker Martinez lashed home his fourth goal of the season in all competitions on the hour mark after a poor clearance from Zeki Celik to give Inter a hard-fought win at the Stadio Olimpico in Rome.
Defender Gabbia rose highest to thump home Tijjani Reijnders' free-kick in the 89th minute and give Milan a Serie A win which pulls them out of a miserable early season slump.
Henrikh Mkhitaryan blazed over the best chance of the match 15 minutes from time.
Inter and AC Milan on Friday rejected the project to modernise and restructure the iconic San Siro stadium which they share, city mayor Giuseppe Sala announced.
Italian club Napoli said they were "stunned" after Italy's football federation (FIGC) on Tuesday dropped a probe into alleged racist comments made by Inter Milan's Francesco Acerbi to Napoli's Juan Jesus due to lack of evidence.
Francesco Acerbi on Monday left Italy's training camp ahead of two friendlies in the United States after reports he will be investigated for alleged racial abuse of Napoli defender Juan Jesus.
Juan Jesus nodded home Napoli's leveller with nine minutes remaining after fighting back from Matteo Darmian's opener shortly before half-time to snatch a deserved point.
Inter moved to 75 points and an 18-point lead over second-placed Juventus, who host Atalanta on Sunday. Bologna are fourth on 51 points after 28 games.
Youngster Kristjan Asllani and veteran Alexis Sanchez scored within six minutes of each other in the San Siro as Inter move closer to going one better than local rivals AC Milan and their Scudetto tally, which would get them a second star above their club badge.
Inter Milan cruised to a 4-0 home win against Atalanta in Serie A on Wednesday, extending their lead at the top of the standings to 12 points as they edge closer to a 20th league title.
Atletico Madrid are hoping Antoine Griezmann's injury is nothing more than a sprained ankle after the forward was substituted in their 1-0 defeat by Inter Milan in the first leg of their Champions League last-16 tie, manager Diego Simeone said.
Inter Milan stretched their lead at the top of Serie A to 10 points on Friday after cruising past sorry Salernitana 4-0 ahead of their Champions League clash with Atletico Madrid.
Juve's title hopes took a hit at the Allianz Stadium in Turin after Lautaro Giannetti poked home the only goal of the game in the 25th minute.
Marcus Thuram was key to Inter's win at a soaking Stadio Olimpico in Rome as, with his team trailing at half-time, the France attacker made it two goals each shortly after the break and forced the Angelino own goal which put Inter ahead in the 56th minute.