The victory, which was Atletico's first against their local rivals since 1999, saw then-manager Jose Mourinho sent to the stands and star man Cristiano Ronaldo red-carded as the visitors to the Bernabeu earned an extra-time win.
Yet even though Atleti and La Liga champions Barcelona have started the new season in blistering fashion, Real look certain to win Spain's most prestigious cup competition.
After joining the club from PSG earlier this summer, manager Carlo Ancelotti has quickly gone about adding to Madrid's already large and highly talented squad of players.
The former Chelsea boss has so far focused on bringing some of Spain's brightest young players to the capital.
The club also decided to exercise a buy-back clause with Spanish right-back Daniel Carvajal, re-signing him from German club Bayer Leverkusen early this summer.
Real have promoted homegrown striker Alvaro Morata from the B team and signed Brazilian youngster Casemiro from Sao Paolo, too.
The importance of strength-in-depth over a long season cannot be underestimated.
Real will likely play more than 50 competitive games between now and May, meaning squads will need to be utilised fully in order to keep players fit, fresh and on form for the duration of the 2013-14 campaign.
But with Ronaldo, Mesut Ozil, Angel Di Maria, Kaka, Luka Modric, Xabi Alonso and Sami Khedira at his disposal, Ancelotti has all the midfield options he needs to launch an assault on the league title and in Europe.
And with plenty of choice in defence and attack too, Los Blancos will be able to field a strong starting XI in every Copa del Rey game they face this season, no matter what the importance of their next fixture.
Fierce rivals Barca will provide stiff competition, of course, as will Atletico and Valencia, but Ancelotti's drive to lift silverware in his first season should lead to him taking the competition seriously enough to achieve success.