Real Madrid coach Zinedine Zidane said his star players were not mentally up to the task after they lost 1-0 to Atletico Madrid in Saturday's derbi clash.
Antoine Griezmann's second-half goal was enough for the visitors to win a third consecutive league win at the Estadio Santiago Bernabeu -- with Cristiano Ronaldo missing Madrid's two best chances to get something out of the game.
Should Barcelona win at home to Sevilla on Sunday evening at the Camp Nou, Madrid will be 12 points behind the leaders with just 12 games remaining, while Atletico Madrid are now four points clear of their neighbours in second place.
Zidane said he took responsibility for what was his first defeat since taking over from Rafa Benitez in January, but he said his team had not been focused enough for a game they knew would be a tough challenge.
"I have the responsibility," Zidane said. "The players play, but I have responsibility. I must look for solutions so it does not happen. I did not expect to lose, this first defeat at home, although we knew it would be difficult. When you have chances, you must put them in, nothing else.
"It was not a physical issue, we have done everything in that part. Today's game was more mental, not physical. They played Wednesday, had less time to recover, and look at the game they played. So it is a mental question -- we lacked a bit of everything."
Zidane sent on three homegrown players as substitutes during the game and appeared to suggest that some big names at the club might be moved on this summer no matter what happens.
"I have full confidence in my players, I am always behind them, they are always behind me, whatever happens," he said. "Next year there might be changes, players and coach. But for now we must keep going as we have something to aim for.
"I told the players they cannot be happy. In a game like this, we have to do more, run more, put our foot in more, do more. If you do not, this will happen.
"We were not ready for the game as we thought we were. We had to run more, but they were able to play comfortably."
Zidane implicitly accepted that his team's chances in La Liga were now very faint, while saying he wanted to get everyone quickly focused again ahead of Wednesday's trip to Levante.
"What is now important for me, and the team, is the next game," he said. "La Liga is not over, but it was difficult before the game. If you lose points it is more difficult. But we will continue, will not give up on his season. We have games to win, things to win.
"Of course it is a difficult moment to lose a derby at home. But we must be professional and think about the next game. Madrid will never give in -- not me nor the players. There can be criticism, but that is part of the game. I will look for a solution -- starting with winning on Wednesday."
Madrid's hopes for a trophy this year now seem to rest on their Champions League campaign, with the team 2-0 up against Roma ahead of their round-of-16 second leg on March 8 at the Bernabeu, but Zidane is not looking past Levante.
"Before the Champions League we have a game -- on Wednesday," Zidane said. "We must prepare for that game, to do everything to do the most we can to win. Our objective, our duty, is to think about the next game. Today is very hard, a very hard blow, to lose at home to Atletico Madrid. It is difficult."
The half-time change which saw Karim Benzema replaced by 18-year-old Borja Mayoral for just his second La Liga appearance was forced after Real's centre-forward suffered an injury, Zidane said.
"Benzema had a problem, he was feeling pain," he said. "He could not sprint, we did not want to take a risk. So he was changed. I wanted Mayoral as needed to put in a nine.
"Borja is playing well, today was his opportunity, I would have liked him to take his chance, but he played well. We are happy with him. He played with personality."