Barcelona: Real Madrid may face opposition from two sides on Sunday when they host Levante in the Spanish league. Besides the rivals on the field, the team's own fans may be force to be reckoned with.
Rarely has a team been booed after qualifying for the Champions League quarterfinals. But the jeers rained down on Madrid's players following a 4-3 loss to Schalke at the Santiago Bernabeu Stadium on Tuesday, when the European champions limped into the next round 5-4 on aggregate.
"Our supporters have the right to boo us," Madrid defender Pepe said. "They know when we are playing poorly, and we have to acknowledge it. Against Schalke we were lacking in attitude. We ran a lot, but each one going his own way.
"Against Schalke we almost hit rock bottom. We didn't take the match seriously and play with the intensity we should have shown."
The humiliating defeat - the first time Madrid has conceded four goals at home in European competition in 15 years - was Madrid's third straight game without a victory.
Those two prior stumbles cost Madrid the league lead, with Barcelona now one point ahead with a match between the two at the Camp Nou coming up.
Here are some things to know about this weekend's matches:
CIRCLING THE WAGONS
Madrid's rapid fall from the juggernaut that ended 2014 with a Spanish record 22-win streak led to club president Florentino Perez speaking on Thursday to dismiss media reports that coach Carlo Ancelotti's job was in danger.
"He has the backing of his president and the board," Perez said. "Whatever happens, he is the coach of Real Madrid."
Perez made a call for unity among Madrid's faithful.
"I ask as president of Real Madrid that they support our coach and players and that they feel proud of them for everything they have given us and all they will give us in the future. They need your support."
Cristiano Ronaldo is the one Madrid player to avoid a stunning slump in form.
His two goals on Tuesday saved his team from an ignominious exit from the Champions League, and a Levante side winless in 10 consecutive away games should provide ample targets for the Ballon d'Or holder.
But Ancelotti will be hoping not only for a victory over Levante, but also a major improvement across the board from his struggling set of stars.
Gareth Bale has gone nine games without scoring a goal, while Karim Benzema's presence had been barely felt in recent matches before his goal against Schalke.
Barcelona is hitting its stride just before what could be the most important week of its season.
Following the trip to Eibar, the team returns for home matches against Manchester City in the Champions League before its league match against Madrid.
Lionel Messi has exploded since the winter break and has made up a 12-goal gap to pull level with Ronaldo as the league's leading scorers with 30 goals each. But the secret to Barcelona's success has been Luis Suarez finally finding his scoring touch with six goals in his last four appearances.
Overall, Messi, Suarez and Neymar have outscored Madrid's attacking unit of Ronaldo, Bale and Benzema 80 goals to 75 this season.
"We are getting to know one another better as the season goes on," Neymar said. "I don't need to say anything about Suarez and Messi. Messi is the best player in the world and Suarez is also among the best."
They will take aim at an Eibar side that has lost seven straight matches.
QUESTION OF PRIORITIES
It may be time for Atletico Madrid to quietly shift focus from keeping afloat its sinking title defense and focus on the Champions League.
After only one win in the last four rounds, the team is seven points adrift before visiting Espanyol on Saturday.
Atletico's hopes of reaching a second straight European Cup final rest on overturning a 1-0 loss at Bayer Leverkusen on Tuesday.