Is Real Madrid midfield solid enough?

Toni Kroos and Isco are two attacking midfielders playing as if they were physical and mentally ready to defend. Furthermore, they are required to contribute offensively once Real Madrid recover the ball, as Ancelotti's team relies a lot on Isco's playmaking abilities. The Italian's light midfield worked very well before the Christmas break with a good streak of wins and a statement 3-1 triumph in El Clásico, but Ancelotti's lack of rotations has finally showed that he might end up needing a pure defensive midfielder to help Real Madrid recover the ball.

Kroos keeps saying he is not tired, but the way his team have struggled at preventing the opposition's attacks suggests otherwise. The German and Isco are not defending properly and both Athletic Bilbao and Villarreal were able to break through Real Madrid's pressing with ease. Is that Kroos or Isco's fault? There's a reason why box-to-box midfielders are usually tall and strong. They cover more ground with less effort. Isco was visibly tired after just 60 minutes in San Mamés, and Kroos still has to learn the position in order to provide support to Real's defensive line.

There are three answers to Real Madrid's woes in the midfield.

1. Illarramendi or Lucas Silva playing deep. That would be giving up on Kroos as a defensive midfielder, and that's clearly something Ancelotti doesn't want. That would not help Real Madrid's ball movement against teams pressing high up the pitch, but that should not be the team's priority right now.
2. Rotations! Again, this midfield got the job brilliantly done when they were fresh. In order for Isco and Kroos to contribute defensively as they are expected to in their positions, they need to be physically ready, and that's why rotations are need to sustain Ancelotti's system.
3. More defensive help from the men upfront. This is the least likely scenario. Although Bale has definitely improved his contribution to a point where he's almost ineffective on offense, Benzema and Cristiano Ronaldo are still relieved of any kind of defensive work.