While the Partenopei progressed to the quarter-finals on Wednesday, La Viola lost deep into extra time against Inter Milan.
Though Napoli squeezed through in the cup against Serie B side Empoli, coach Gennaro Gattuso criticised his much-changed team after their 3-2 victory for allowing their enterprising opponents too many counter-attacks.
Last weekend's win at Udinese was a similarly close-run thing, as Lorenzo Insigne netted a penalty to move onto seven goals for the campaign - the same haul as Hirving Lozano, who has been particularly impressive of late.
With the diminutive pair's help, sixth-placed Napoli have registered 18 goals in the last half hour of Serie A matches this season - only free-scoring Inter have struck more after the 60th minute, with 23.
Napoli's prowess late in games - demonstrated most recently through Tiemoue Bakayoko's winner in Udine - reflects their determined spirit under Gattuso and should serve as a warning to their next opponents Fiorentina.
Although Cesare Prandelli's side suffered heartbreak as they were turfed out of the Coppa Italia by Inter substitute Romelu Lukaku on Wednesday night, the Tuscan club's Serie A form has picked up in the aftermath of a shock 3-0 win over Juventus before Christmas.
The Viola turned over Cagliari at home last time out in the league, largely thanks to the heroics of two of their top performers of a trying season so far.
Serb striker Dusan Vlahovic's strike helped coach Prandelli - who has overseen an uplift in Fiorentina form since his return to the dugout in December - seal victory following indomitable goalkeeper Bartlomiej Dragowski's earlier penalty save.
A scorer in their last encounter against Napoli, almost exactly a year ago, Vlahovic is one of just four players (within the top five European leagues) born since 2000 to have found the net at least six times so far this season, alongside such luminaries as Erling Haaland, Moise Kean and Nice striker Amine Gouiri.
His fifth goal in the last six matches has seen Prandelli's patience with the young striker being richly rewarded and that hot streak has helped Fiorentina to a respectable run of seven points from four games.
Looking for back-to-back wins for the first time in Serie A this season, they now take on a Napoli outfit that have shown some chinks in their armour in recent games.
Napoli Serie A form: LLDWLW
Napoli form (all competitions): LDWLWW
Fiorentina Serie A form: DDWDLW
Fiorentina form (all competitions): DWDLWL
Gennaro Gattuso is without first choice full-back Giovanni Di Lorenzo, who is suspended, so Elseid Hysaj should cover on the right of Napoli's four-man defence, from which mainstay Kostas Manolas will also be missing due to a thigh strain. In the absence of Manolas, Nikola Maksimovic is favoured over Amir Rrahmani to join Kalidou Koulibaly in the centre.
As Victor Osimhen is still positive for COVID-19, Andrea Petagna should provide a front line focal point, assisted by the lively trio of Hirving Lozano, Piotr Zielinski and Lorenzo Insigne. Dries Mertens could feature from the bench ahead of the much-anticipated engagement with Juventus in the Suppercoppa Italiana next week.
Fiorentina have doubts over the fitness of veteran pair Franck Ribery and Borja Valero, with captain German Pezzella expected to return to the centre of a three-man defence having overcome a thigh injury.
Dusan Vlahovic will reclaim the centre-forward role from Christian Kouame, despite the Ivorian's cup goal against Inter, having now established himself as number one in the pecking order.
Napoli possible starting lineup:
Ospina; Hysaj, Manolas, Koulibaly, Rui; Bakayoko, Ruiz; Lozano, Zielinski, Insigne; Petagna
Fiorentina possible starting lineup:
Dragowski; Milenkovic, Pezzella, Igor; Caceres, Amrabat, Pulgar, Castrovilli, Biraghi; Callejon; Vlahovic
We say: Napoli 1-1 Fiorentina
A renewed Fiorentina squad can take home a point from the trip down to Naples, as their greater solidity of late has been complemented by a particularly clinical period for Dusan Vlahovic.
Napoli's lingering title hopes have been undermined by recent inconsistency and that may continue at the Maradona on Sunday - with perhaps half an eye on the upcoming Supercoppa showdown with Juve.