Xavi claims his side lacked ruthlessness in front of goal.
Summer signing Robert Lewandowski struggled to find the back of the net against his former side Bayern Munich on Tuesday night.
Pedri also hit the woodwork when Barcelona was already 2-0 down.
“We were better than Bayern in many aspects,” Xavi said. “We were better physically and we dominated the first half. I’m angry because it was a day to win. It’s a learning experience, but it’s hard. We didn’t score despite having seven clear chances. You have to score them. I’m pissed off but proud.
“It’s also about effectiveness. You get in front of the goalkeeper and you have to score. The first half was excellent, we had them in their half, we dominated them and we won duels. We deserved to win.
“To learn from our mistakes. When the situation is bad, you learn. You can’t go 1-0 down from a corner like that. They shouldn’t be able to go inside on a counter-attack. We have to learn. We’re leaving with a 2-0 scoreline, which is not what we saw on the pitch.”