Atletico Madrid won the Saturday decisive match against Catalan giants 1-0.
Barcelona manager Ronald Koeman was left feeling worried by the way Atletico Madrid found the way to the back of the net at Wanda Metropolitano.
Barcelona travelled to Madrid with only one victory in their last five LaLiga games, and defeat against Atleti could take them to the bottom half of the Laliga table.
Yannik Carrasco scored the solitary goal from 35 yards into an empty goal for Atelico at the end of the first half when Gerard Pique failed to intercept Angel Correa’s pass, and Mark-Andre ter Stegen was unable to stop Carrasco.
Ronald koeman is left frustrated.
"It is worrying," he told Movistar. "For a big team, conceding a goal like this ... it can't be, because it's the 47th minute, we had the ball and then they score, 1-0.
"We controlled and we knew that it was difficult to create many chances. We had a pair and with the score 0-0, the game would have been totally different [if they had taken either chance].
"Like any coach, I am responsible for the team's results."
Ateltico’s win put them nine points ahead of Barcelona and Koeman consider it as a big gap and it needs a winning streak from his men to compensate.
"It's a pretty big difference, but there is a lot of the league left and a lot of games," he continued.
"We know that every match is complicated, but after this defeat we have to chain an important winning streak.
"I have seen a team that has fought until the last second to been able to level the game, so in this sense I am not worried."
Gerard Pique was diagnosed with a knee sprain and further tests are needed to find out the extent of the injury.