Barcelona will do everything they can against Valencia, and I believe they will prevail. Barcelona needs to drop fewer points to win the title this year. They've already dropped two points. The Spanish league will be in full swing. This year, the race will continue alongside Real Madrid. We all know Valencia is a dangerous team. It must be difficult for Barcelona to suffer a surprise drop. If they don't want this to happen again, they absolutely must win this match.
Barcelona don't want to lose points now after they drew with Rayo Vallecano, because every next loss of points will give Real a reason to increase the gap. Valencia lost to Osasuna in the first match away, I think it will be even more difficult for them against Barcelona away, so yes, Barcelona should win this match. But the odds are too small for a win, so this match will be combined with other matches. But I'll probably just skip this match and see how Barcelona plays, I want to make sure that everything is okay with them.
I'm almost certain it will be a smooth match for Barcelona. Valencia isn't a team that can challenge them. They need to win every match to close the two-point gap with Real Madrid. They have an El Clasico derby in October. If they don't drop any points until then, they might be able to catch Real Madrid in that match. They'll also be weighing up the possibility of Real Madrid dropping points during this period. Barcelona's responsibility is to try to win every match.