Pique admitted that Barcelona fell apart in the second half and that his side can have "no excuses" over the result.
"We are Barcelona and we have to fight back," Pique told the club's official website.
"We had the match under control in the first half but we didn't play well in the second. We fell apart after they scored the opener, it was out of control. We have to improve and learn from this.
"There are no excuses, the pitch, the referee, nothing, we have to work hard to fight back."
Pique has played 25 games for Barcelona this season.