He added, praising the French opponent: "The opponent has high quality in attacking transitions. We tried to defend against them and we did that well, but in the last 15 minutes, we did not have our full energy."
He continued: "This is not an excuse. Perhaps the preparation for this match was not optimal, but now we have to analyze things. We need to improve in the future, although today we did many things very well."
The German coach praised full-back Xavi Espart, who scored a goal for Barcelona, saying: "Espart played a wonderful match, as he scored a goal, and the level he is playing at is truly amazing."
Regarding the condition of Dani Olmo, who left injured, Flick said: "We will see what happens regarding Olmo. He suffered a bruise, so we have to wait to know the development of his condition."
Barcelona will be required to recover quickly from the defeat before facing Real Madrid in El Clasico next Sunday.