#1 Alvaro Morata
Out of all the departures, this is, possibly, the most unjustified because of how good Alvaro Morata played on his return to Real Madrid in 2016. The victim of a buy-back clause execution, he came back to his boyhood club in search of glory, and he would've achieved his deserved starting place had it not been Zidane's blind trust in misfiring Karim Benzema.
The Spaniard scored important goals for Real Madrid at crucial points in the season, but Zidane was adamant in his decision to start the Frenchman regardless of all the stats. This controversial choice was linked to the need of a striker who drops back often, which was more characteristic of Benzema than Morata.
On the back of a string of strong showings from the bench, the Spain international took confidence in his ability and left for England last summer, to play as the main striker at Chelsea.
Morata had his reason to leave but we can't say the same about Zidane's reason to let him go as Real, unsurprisingly, now suffer from a dearth of good substitute strikers. The only central striker option, in absence of Benzema, is Borja Mayoral---a player not on par with his predecessor.