While the young Spaniard was struggling to break into Pep Guardiola's first-team, his reputation was that of one of the finest young talents in world football.
And after a very slow start to life in the Spanish football, Diaz is beginning to show why Los Blancos decided to recruit him in January.
Zinedine Zidane has finally handed Diaz the opportunities he deserves, handing him his second start in four league games last night against high-flying Getafe.
Lining up on the right-hand side of attack alongside Karim Benzema and Gareth Bale, the 19-year-old was the star of the show for Real.
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He was the only player taking the game to Getafe - who are currently in the Champions League places - and he produced some outrageous skills throughout his performance.
You can watch the short montage of his dazzling moves below.
You can see why fans were likening him to Bernardo Silva last night...
The invention and craft shown by Diaz is exactly the kind of thing Real have been lacking throughout the campaign.
Much like Vinicius Junior, Diaz's injection of youthful unpredictability and fearlessness is exactly what this stale Los Blancos side need going forward.
If Zidane can manage to hand significant game time to both young stars next season, the fans will likely be even more on his side.
Of course, there will be issues trying to manage their game time alongside the likes of Isco, Marco Asensio, Lucas Vazquez, Bale and potential summer arrivals.
If Eden Hazard is also to arrive from Chelsea, both Diaz and Vinicius will be spending more time on the bench.
But in what has been a dismal season for the club, the two youngsters are at least two rays of light.News Now - Sport News