With five games to go, Barca have an eight-point advantage over their fierce rivals Real Madrid.
Even so, Guardiola feels tomorrow's match is crucial.
"It's an absolute priority," he told the club's website. "We have to be very aware that much of the league title depends on what we do at what is always a tough ground.
"If we don't focus our five senses on that, we won't do it.
"Tomorrow we're playing for a competition that lasts 11 months.