Bilbao coach Joaquin Caparros said: "If you are not effective on a ground such as this, you will never be able to compete.
"We tried our best, but we wasted a few chances and in the end, we paid for it against a ruthless team like Barcelona, who possess a lot of impressive quality.
"We tried to regroup after going 2-0 down and we even had an opportunity to hit back, but Barca managed to overcome us. When they have so much space to work with, it's just terrible.
"We always wanted to compete with them and never once did we surrender. We would've liked to score a few more goals, but the result is there for all to see and we must accept it."