Villarreal forward Giuseppe Rossi is a major doubt for the game after injuring his knee in Saturday's 1-1 draw with Athletic Bilbao while Marco Ruben has been ruled out for the next three weeks after breaking his toe in the same game at San Mames.
The Yellow Submarine lost its Group A opener 2-0 to Bayern Munich and the club have said they will make a last minute decision on whether to include Rossi in the squad for their crunch game in Naples.
As a result, coach Juan Carlos Garrido could decide to throw Javier Camunas into the attack to partner Nilmar if Rossi fails a late fitness test.
Meanwhile, Napoli coach Walter Mazzarri fielded his strongest available side in their goalless Serie A draw with Fioretina at the weekend - including playing Edison Cavani, Serie A's leading goalscorer last season.
Napoli began their Group A campaign with a credible 1-1 draw with Manchester City.