If you look at the statistical data, Barcelona should be able to beat Velencia because this club is not very strong, especially as Velencia is not in good condition lately and has experienced 3 defeats from the last 5 matches. I think Barcelona can take advantage of opportunities when Velencia's condition is not good and I am sure Barcelona is capable achieved victory in this match.
Competing as a guest of course, Barcelona will experience a little difficulty against Valencia, even though from the statistics Valencia doesn't look consistent because they played very badly in their previous match, but in the match against Barcelona, at least Valencia must play as hard as possible to not lose points, at least they can balance Barcelona's game and share. points with Barcelona.
Barcelona are also not completely in good condition, especially considering yesterday's defeat in the UCL when they visited Antwerp, they were defeated 3-2, even though in the end they still qualified for the next round in the UCL, Xavi had to really put pressure on the players to get full points, especially The previous defeat also against Girona, they had to lose points, against Valencia at least Barcelona must be able to get full points to be able to maintain their position in the current standings.
Even though it home match for Valencia, they still won't be able to easily beat or draw against Barcelona in this home match, this match is very important for Barcelona to be able to get full points in order to catch up with 3rd place.
Atletico Madrid occupies 3rd place with 34 points, the same as Barcelona and by winning the match against Valencia, Barcelona can take over that position.
Moreover, Valencia is also not strong team and everything can be clearly proven because in 16 matches they were only able to have 5 wins with 7 defeats, this is proof that Valencia is not an opponent who can beat or hold Barcelona to draw.
Barcelona defeat in the UCL match will never affect anything because they still qualify for the last 16 and of course this defeat is only gift for Antwerp because they are at the bottom of group H.
We cannot assess and determine match results or predict team performance when competing in the Domestic League just from the results of UCL games, the difference will be very visible.
Barcelona will still be able to perform well and beat Valencia in this weekend match.
The favorite team will still be the favorite and defeat to ajust weak team is just surprise that cannot possibly be repeated in two consecutive matches.