Seven top-class players for only three places in the starting lineup if Zidane maintains the 4-3-3 formation. Modric, Kroos, Casemiro, Isco, Kovacic, Marcos Llorente and new signing Ceballos will fight for a spot in Real's midfield.
On the day Real Madrid reached an agreement for the Betis midfielder, Tottenham's efforts to sign Mateo Kovacic have also come to light.
The Croatian made 39 appearances last season, but was never Zidane's preferred option, always playing second fiddle to the likes of Modric, Kroos or Casemiro.
Marcos Llorente's arrival could see Kovacic dropped, as the defensive midfielder, who was loaned out to Alaves last season, is the Brazilian's natural alternative.The same would happen with Ceballos in Modric and Kroos' position.
Real Madrid splashed out £25 million for the Croatia international two years ago, and the player is considered a vital part of the club's future.
Tottenham want to take advantage of Real Madrid's crammed midfield and the Spanish club would only consider selling Marcos Llorente or Kovacic, always with a buy-back clause.