The midfielder could miss the rest of the season and possibly the FIFA World Cup after sustaining a cruciate ligament injury in his right knee in Germany's friendly with Italy on Friday.
Real coach Ancelotti confirmed he is exploring various possibilities, with Asier Illarramendi, Casemiro and Isco all pushing for inclusion alongside Xabi Alonso.
"We have tried to use the same system in recent games, with two defensive pivots," he said on Friday. "We can use Casemiro and Xabi Alonso as defensive pivots to Illarr (Illarramendi) or (bring in) offensive midfielder Isco.
"Everyone gives me confidence. I will make a decision tomorrow."
The Italian sees his side resume their domestic campaign after the international break, but his squad will be depleted as Marcelo, Raphael Varane (both knee), Angel di Maria (hamstring), and Fabio Coentrao (thigh) are all sidelined.
Ancelotti confirmed these injuries are a concern, but believes Real's squad is mentally prepared with many of his players buoyed by qualification for the World Cup with their countries.
He added: "The physical state of the squad is not good, because we have several players who will not be available tomorrow. Di Maria, Khedira, Marcelo, Varane and Coentrao - five casualties.
"(But) the mentality of the players is good. Everyone is focused on the game tomorrow. They have arrived happy because they have achieved a pass to the World Cup. Psychologically the state of the players is good."
The former MIlan, Chelsea and Paris Saint-Germain manager was particularly disappointed with Spain's decision to play friendlies in Equatorial Guinea and South Africa, and feels more care should be taken to reduce the risk of injury.
"It's hard for me to talk about this, but I think the organisation for Spain's friendlies was not good because the players slept three nights on the plane," he commented.
"Barcelona had an injury to (Victor) Valdes and we (had) none, but a better overall organisation can help prevent injuries."
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