Busquets today spoke of the need to "correct the mistakes".
He said: "Last year we also began with problems, losing to Hercules, but it's no good worrying about it.
"We have to take note of it, correct the mistakes, and think from today about the Champions League and AC Milan (on Tuesday night).
"At half-time we didn't think at all that the game was won, and it turned out like that.
"It's a fact that away from home winning is always tough and will get increasingly tougher. We haven't had the chance to talk about what happened yesterday but we will."
Most of the Barca squad were away on international duty last week, and Spain international Busquets believes that may have been a contributing factor.
He added: "It's always tricky. You come back from another setting, another team, and different team-mates.
"It's not easy to get back to what we do well, but we can't let it happen again."