Ronaldo has recovered from a niggle and fellow forward Bale was suspended for the match.
Central defender Raphael Varane is out with a thigh problem.
Napoli, 3-1 down after the first leg, have winger Dries Mertens available who has recovered from a knock.
Mertens scored twice in the 2-1 Serie A win at Roma at the weekend, as Napoli narrowed the gap on the second-placed side to two points.
Round of 16 fixtures today:
20:45 Arsenal ? – ? Bayern Munich
20:45 SSC Napoli ? – ? Real Madrid
