The Galaticos welcomed third-tier Numancia as Real sought for team redemption after been held to a disheartening 2-2 draw away at Celta Vigo.
Zinedine Zidane's selection were held to a 2-2 draw as defensive frailty cost them the game.
The Los Blancos' took the lead on two occasions through Lucas Vazquez, only to surrender their advantage to a sturdy Numancia.
Here are the lessons that can be drawn from the game.
Real Madrid progresses
The home side progressed despite been held to a 2-2 draw at the Bernabeu Stadium following a convincing 3-0 win away from home in the first leg.
Perhaps there was a bit of complacency in the team selections as Madrid might have felt that the job had been done in the first leg. Key players were rested and some returned from injury and this might have contributed to an unexpected low-level performance by Madrid.
However, they must improve for the next rounds of the competition.
Lucas Vasquez delivers for Real
The talented Spanish forward took his time to ensure that Real’s complacency do not end in a defeat despite their obvious advantage in the course of the tie.
Without Gareth Bale and star man Cristiano Ronaldo and a host of first team regulars, Real had to lean on Vasquez shoulders in order to secure the game.
Vasquez took his first goal expertly and was at the right place and time to poke in the second. The forward delivered in the absence of some key players, but Real are going to need an extra man or two to do the same if they are to get away with resting players like that in the coming rounds.
Warning to Zinedine Zidane
Whether it was due to complacency or regards to Real’s performance in the Copa Del Rey tie or a reality of Real recent slump there is a need for Zidane to treat the situation with caution.
The Los Blancos' managerial seat is a renowned and costly one, and the Former Ballon D’Or winner must take steps to improve the team’s performances, perhaps by scooping into the transfer market.
A lower-side like Numancia getting two goals past Real goes a lot to show about the clubs current state in the campaign.
They have been experiencing difficulties up front, and now Numancia has revealed their frailty at the back. Time for Zidane seems to be running out.