Real Madrid have become complacent while watching Barcelona "reinvent themselves", according to former midfielder Victor Sanchez.
La Liga leaders Barca were held to a surprise 0-0 draw by Getafe on Sunday, but still hold a 17-point lead over the champions, who sit fourth.
Madrid also suffered a shock Copa del Rey exit at the hands of Leganes and must beat Paris Saint-Germain in the last 16 of the Champions League if they are to keep alive their hopes of a third successive triumph in Europe.
Victor, who progressed through Madrid's youth ranks and won La Liga and the Champions League with the senior team, believes his old club have paid the price for resting on their laurels this term.
"Complacency is the biggest enemy of high performance," he told AS.
"Real Madrid were in an uncomfortable place for a few years because they had to try to compete with the best ever Barcelona team. That situation is a motivating factor in itself, it makes you be more proactive and keeps you out of the comfort zone.
"In the last two years, Real Madrid managed to achieve their target, becoming the number one team with a quality squad which allowed the coach to put out two completely different starting line-ups capable of competing at the highest level.
"What has happened since they achieved that success? Performance levels have dipped. While Barca have reinvented themselves, thanks to their newfound motivation to get back to the top, Real Madrid seem to have let complacency creep in. You need to combat complacency."
Victor feels head coach Zinedine Zidane must do his part to stamp any arrogance out of the squad, having steered Madrid to eight major trophies in two years in charge.
"It's obviously one of the coach's responsibilities, but the director of football and his staff also share part of that responsibility," said Victor, who was sacked by Real Betis in May last year.
"They need to work within a defined strategic framework, so that everyone is working in the same direction. That's one of the most difficult and exciting parts of our job. You have to maintain high levels of motivation, effort and commitment...you have to keep those levels as high as possible and avoid the natural human tendency to relax once you've achieved a target.
"You have to fight against complacency and stop anyone from entering the comfort zone. When you get that right, the players grow and their performances improve and you also help the club increase the value of its most important assets, its players."