#3 Overlooking young talents like Hakimi and Hernandez
Real Madrid had some incredibly talented young players such as Achraf Hakimi and Theo Hernandez in their books.
But right now, neither of them are at the club and are instead flourishing elsewhere.
Hernandez wasn't given enough chances to shine, something he recently revealed once again. He has since gone on to become a key player in a rejuvenated AC Milan team under Stefano Pioli.
The right-back has scored 12 goals and made 11 assists for the Rossoneri since last season, while Mendy is yet to fully justify his €48 million price tag at Real Madrid.
Meanwhile, Hakimi is fast becoming a world-class right-back at Inter Milan, scoring and assisting six times apiece and bringing a new dimension to the Nerazzurri attack.
#2 Spending €100 million for Eden Hazard
Eden Hazard's much-touted move to Real Madrid finally materialised in 2019 as the Chelsea legend arrived at the Santiago Bernabeu on a €100 million transfer.
Many great things were expected of him, but unfortunately, injuries have constantly hampered his spell with the Spanish giants so far.
Hazard has missed 50 of Real Madrid's 86 games since joining the club. He is now set to face another four to six weeks on the sidelines after only returning from a lengthy absence last weekend.
There's no doubting Hazard's quality as a player, and he still has time to turn things around. But at the moment, the 30-year old is turning out to be an expensive flop at Real Madrid.
#1 Letting Cristiano Ronaldo go
Whether it was a rift, arrogance or pure stupidity, Real Madrid's decision to sell Cristiano Ronaldo will go down in history as one of the worst by any club.
The last three years have produced enough evidence to suggest that Ronaldo's exit hasn't worked for both parties, especially Real Madrid.
While Los Blancos stare at the possibility of another trophyless season, Ronaldo's heartache in Europe continued after another disappointing exit from the Champions League.
According to the Portuguese ace, a breakdown of relationship with Perez precipitated his departure. But clearly, there have been no winners here.