Sergio Busquets has admitted that Barcelona's 1-0 loss to Real Valladolid on Saturday was "painful".
The defeat left the Catalan outfit in third position in the table, one point from La Liga leaders Atletico Madrid.
However, second-place Real Madrid would move four points clear with victory over Levante at the Bernabeu this evening.
"It's been a hard day. There's very little left in the League and we can't afford to drop points. Four points could be a big difference," he told reporters at a press conference.
"La Liga has gotten more difficult. We didn't play well and it's a new competition so we have to think about it differently. We have to learn from our mistakes.
"We need to be eager right from the start, to be better than our opponent. That's what we've been looking for. We need to go to Santiago Bernabeu looking to win. This is a painful defeat and we were poor but we need to start thinking about the Champions League now."
Barcelona have lost four of their 27 league games this season.
