Before Saturday evening they had lost just once at home in La Liga and were proud owners of the league's meanest defense.
Their cause was further strengthened when Jose Mourinho made eight changes and, even more so when Radamel Falcao headed them in front inside five minutes.
Derby day gloom was soon restored for them though, unfortunately.
Before 10 minutes was up, Real Madrid were level. Angel Di Maria's free kick deflecting off Juanfran into the full back's own net.
Di Maria would later score the winner too. His clever run was picked out by Karim Benzema, and the Argentinian international did the rest.
It wasn't all about Di Maria, who became a father this week, though. Here are the player ratings for the rest of Los Blancos' team.
Diego Lopez: 6
One of the three starters retained from the defeat to Dortmund, Lopez didn't have a bad game. He did spill the ball to Diego Godin, who then set up the Atleti goal, but he made a couple of saves and collected a high number of crosses from the home side's wide men.
Michael Essien: 7
Filling in at right-back once again, Essien put in a solid 70 minutes before being replaced by Raphael Varane. He made one vital challenge on Diego Costa, completed 75 percent of his tackles and was successful in all of his aerial duels (via Squawka).
Raul Albiol: 7
It looked like it might have been a long evening for Albiol when Atletico flew out the blocks, and he was booked within the first 10 minutes. He recovered fairly well though, rarely looking overly troubled by an Atletico attack which lacked a punch.
Ricardo Carvalho: 7
A solid enough performance from Carvalho, who seems happy enough with his role at Los Blancos now. He didn't actually make any tackles, but made four interceptions—one late on was particularly key in preventing Diego Costa a free run on goal.
Nacho Fernandez: 6
The young defender was arguably at fault for the Atleti goal. While the line pushed up, he dropped and played everyone onside. It didn't effect him though, he carried on to put in a performance which didn't suggest he had spent most of the season in the B team.
The Portuguese international was in a more advanced position than against Borussia Dortmund, alongside Sami Khedira. He threw himself into plenty of tackles, earned a yellow card and was generally busy. One challenge on Diego Costa in the Madrid box was particularly key.
Sami Khedira: 7
Alongside Pepe and Lopez, Khedira was another starter retained from Wednesday's defeat in Dortmund. He was as close to his normal, steady self as ever in completing three interceptions, two clearances and winning 100 percent of his battles in the air (via Squawka).
In the advanced position often afforded to Mesut Ozil, Kaka had another disappointing night by his standards. He was replaced by Xabi Alonso after 67 minutes and left the pitch having completed just 67 percent of his 18 passes and generally just floating about (via whoscored.com).
Angel Di Maria: 9
Di Maria was involved in three of Real's best chances. His free kick led to the equalizer, a bursting run with the ball through the middle and pass created a wonderful chance for Karim Benzema and he scored the winner after an intelligent run without the ball.
Karim Benzema: 7
Will rue his missed chance in the first half, when he was one-on-one with Thibaut Courtois, but was industrious throughout the 90 minutes. The goals aren't quite coming at the moment, but his clever pass picked out the run of Di Maria for Madrid's second goal.
Alvaro Morata: 8
A wonderful performance from the young forward, who worked extremely hard but perhaps lacked when it came to his decision making—that should come. Dragged one shot wide in the first half, when a cross seemed the best option, and forced a good save from Courtois, after a surging run, in the second.
Xabi Alonso: 6
Replaced Kaka after Madrid took the lead and steadied the ship to see them over the finish line, completing 20 of his 22 passes (via Squawka).
Raphael Varane: 6
Came on for Michael Essien with just under 20 minutes to go. Made a couple of clearances and interceptions as Atleti attempted a comeback.
Luka Modric: 5
Gave the ball away cheaply a couple of times, but was only on the pitch for just over 10 minutes, presumably giving Angel Di Maria a rest ahead of Tuesday's return with Dortmund.
Not used: Iker Casillas, Mesut Ozil, Jose Callejon, Gonzalo Higuain