Barcelona's creaking confidence has added new life to the Primera Liga title race and all eyes will be on the Calderon on Sunday when the leaders visit the unpredictable Atletico Madrid (1800 GMT).
A comeback draw away to Real Betis, a shock home defeat to city rivals Espanyol, and another comeback draw away to Olympique Lyon in the Champions League have shattered the illusion of Barca's invincibility.
Their lead at the top has been cut from 12 points down to seven with chasing Real Madrid on a nine-match winning streak, and the belief is growing in the capital that they can overhaul their arch-rivals to snatch the title as they did in 2007.
Pep Guardiola's team have already beaten Atletico three times this season, giving them a 6-1 league drubbing at the Nou Camp, and winning both legs of a King's Cup last 16 tie.
Seventh-placed Atletico are hardly in the best of form with one win in 11 in all competitions since the turn of the year and were held at home by Porto in the Champions League on Tuesday.
They are struggling to adapt to a change in tactics under new coach Abel Resino and there is growing media speculation that the out-of-form Sergio Aguero is unsettled.
The Argentina striker was substituted early in the second half against Porto to whistles of protest from the home fans, and to his obvious dismay.
"Taking Aguero off was not a good decision because he was playing a good game. He is a reference for us within the team and he should always be there," Atletico midfielder Maniche told radio station Onda Cero afterwards.
Atletico came from behind to beat Barca 4-2 at the Calderon in the league last season, however, and have a reputation for rising to the occasion against the Catalans when it best suits their city rivals Real Madrid.
The champions had a head of steam going before their Champions League meeting with Liverpool, but the 1-0 defeat at the Bernabeu as given them a sudden reality check.
On Saturday, they visit struggling Espanyol (2100) who received a massive lift with their abrasive 2-1 victory over Barca in the city derby.
"It was a turning point for us. We gave one of the best teams in Europe a lot of problems and now we need to do the same against Madrid. It is the way forward," said striker Luis Garcia.
Third-placed Sevilla visit their King's Cup semi-final opponents Athletic Bilbao on Saturday (1900). The Andalucians have a 2-1 first leg lead from last month, and can test the atmosphere at San Mames ahead of next week's second leg.