Yannick Carrasco scored the only goal of the game, in the 3rd minute of first-half's stoppage time as he took the ball around Barcelona goalkeeper Ter Stegen, who had raced high up the field to block an Atletico counter, and fired a shot into an empty a net. That blunder proved costly as Atletico took all three points and sit second in LaLiga points table, while Barca languish at a lowly 10th place.
Koeman was understandably disappointed at how they conceded the goal, and he expressed it afterwards. "We played well in the first half, but a team like Barcelona cannot concede a goal in the 47th minute like we did," the Barca gaffer said [via Marca] in a post-match interview.
Speaking about Barcelona's performance in the match, Koeman said: "The players are working well, but we want better results. In principle we have done our best. Then we had two very clear chances to equalise. It's always difficult, we know that Atletico defend very well. The goal [we conceded] was our fault; it's not good and it can't happen."