A Victor Osimhen header proved enough for Napoli to beat Serie C side Pro Vercelli, but Diego Demme needs tests for his knee injury.
The game started badly for coach Luciano Spalletti, who saw Demme carried off by medical staff after a rough tackle left him with a right knee injury.
A statement from the club confirms more tests will be performed tomorrow, suggesting they fear possible ligament damage.
There was just one goal, as a Mario Rui corner was knocked on by Amir Rrahmani for the Osimhen header.
Zedadka was unlucky to hit the woodwork when sent clear on goal by Osimhen, but the Nigerian striker missed an open goal after the restart.
Osimhen did seem irritable and had tense words with both his teammates and the opposition defenders, who he felt were being too rough for a friendly.
Napoli: Contini (Idasiak 73); Zanoli (Manolas 73), Rrahmani (Malcuit 73), Koulibaly (Gaetano 62), Mario Rui (Luperto 62); Lobotka (Ciciretti 62), Demme (Folorunsho 18); Politano (Machach 62), Ounas (Zielinski 73), Zedadka; Osimhen (Costa 62)