Francesco Calzona is expected to bring Napoli back to a 4-3-3 formation with Victor Osimhen, Matteo Politano and Kvicha Kvaratskhelia, but has a major doubt in midfield against Barcelona.
It kicks off at the Stadio Diego Armando Maradona on Wednesday at 20.00 GMT.
The second leg of the Champions League Round of 16 is at Camp Nou on March 12.
Walter Mazzarri was fired yesterday, himself having replaced Rudi Garcia in October, so Calzona becomes their third coach of the season.
A former assistant manager to both Maurizio Sarri and Luciano Spalletti here, he is therefore expected to permanently shelve the three-man defence and return to the 4-3-3 formation.
He also has Osimhen back for the first time since leaving in late December for the Africa Cup of Nations, where Nigeria lost the Final to the Ivory Coast.
However, Piotr Zielinski was cut from the Champions League squad list in January after refusing to sign a new contract, so it will be either Jens Cajuste or Hamed Junior Traore in midfield.
Mario Rui is expected to return at left-back, with Amir Rrahmani and Juan Jesus the favourites in the centre of defence.
Barcelona had a few worries about Joao Felix, but he took part in the full training session at the Stadio Maradona tonight and should be available.
He might not necessarily start, though, while Inigo Martinez is the favourite to play in defence rather than 17-year-old Cubarsi.
The attack is the worrying area for any opponents, including Robert Lewandowski, Pedri and Lamine Yamal.
Marcos Alonso, Ferran Torres, Gavi and Alejandro Balde are long-term absentees.
Napoli (4-3-3): Meret; Di Lorenzo, Rrahmani, Juan Jesus, Mario Rui; Anguissa, Lobotka, Traorè; Politano, Osimhen, Kvaratskhelia
Barcelona (4-3-3): Ter Stegen; Koundé, Araújo, Íñigo Martínez, Joao Cancelo; Gündogan, Christensen, de Jong; Lamine Yamal, Lewandowski, Pedri