Napoli have two midfield question marks going into the Bernabeu, while Real Madrid are expected to start Lucas Vazquez in the trident.
The first leg in the Champions League Round of 16 kicks off on Wednesday at 19.45 GMT.
Real Madrid are the reigning champions of Europe and the World, having won the Club World Cup in December.
Gareth Bale is out injured and Luka Modric not 100 per cent fit, as he only just returned from an injury lay-off.
Cristiano Ronaldo is fine to start despite picking up a knock against Osasuna at the weekend.
Napoli have two midfield question marks going into the Bernabeu, while Real Madrid are expected to start Lucas Vazquez in the trident.
The first leg in the Champions League Round of 16 kicks off on Wednesday at 19.45 GMT.
Real Madrid are the reigning champions of Europe and the World, having won the Club World Cup in December.
Gareth Bale is out injured and Luka Modric not 100 per cent fit, as he only just returned from an injury lay-off.
Cristiano Ronaldo is fine to start despite picking up a knock against Osasuna at the weekend.
Lucas Vazquez is widely expected to be given the starting spot rather than Isco, joining Ronaldo and Karim Benzema.
Zinedine Zidane has used a 3-5-2 system at times this season, but is likely to go back to the traditional 4-3-3 for such a big game.
It also mirrors Napoli’s tactical shape and Maurizio Sarri assured he had absolutely no intention of changing his all-attack approach.
“My only doubt is whether to start three strikers or four,” mused the Coach in his Press conference today.
That could well be a reference to Piotr Zielinski, who is the more creative option in midfield rather than Allan.
There are also reportedly question marks over another midfield slot, as Amadou Diawara has the upper hand over Jorginho, providing a grittier presence.
Arkadiusz Milik and Leonardo Pavoletti are yet to fully recover from long-term injuries, so there’s no doubt the front three will have Lorenzo Insigne, Dries Mertens and Jose Callejon.
Real Madrid (probable): Navas; Carvajal, Varane, Sergio Ramos, Marcelo; Modric, Kroos, Casemiro; Lucas Vazquez (Isco), Benzema, Cristiano Ronaldo
Napoli (probable): Reina; Hysaj, Albiol, Koulibaly, Ghoulam; Zielinski (Allan), Diawara (Jorginho), Hamsik; Callejon, Mertens, Insigne