Midfielders
This is where Real's cracks are the most visible. Modric's age shows when asked to play with Toni Kroos in a double pivot, and the German is no bustling engine either. Both are still very high calibre players, but the days of when they could manage a bit of everything seem to be behind them. They will still manage more complete performances on some days, but can't be expected to do so consistently.
This is where the reliance on Casemiro is striking. The Brazilian has been able to fill gaps where the duo have lacked and Zidane can afford to lean on him at the moment. Even any injury issues could be bayed by the presence of the Uruguayan Federico Valverde who has shown that he can play a similar role to Casemiro, whether at the base of a midfield three or in a double pivot alongside Kroos or Modric.
Last season we saw Kroos, Modric, and Casemiro in the middle of the pitch for most of the season. Despite poor results, none of the trio lost their place in the side, but with a change of system this time around, it could mean more time on the bench for one of them. Isco could be considered to replace Kroos in a midfield trio, but in a double pivot, Isco would be suited to a role further up the pitch.