The title favourites started their campaign with a 7-0 thrashing of Levante but have looked less impressive since and picked up the Spanish Super Cup on away goals in midweek after a goalless draw with Atletico Madrid.
Neymar made his full debut against Atletico and his struggle to link up with Lionel Messi was plain to see - but it does not unduly worry Martino heading into the weekend.
Martino said: "They (Neymar and Messi) played quite well but it is true they didn't come together a lot. However I have no doubts they are two players who will work well together in the future."
Miroslav Djukic's Valencia have had a mixed campaign so far after winning their opener against Malaga before crashing to a 3-1 defeat away to Espanyol last Saturday.
And midfielder Oriel Romeu knows his side will have to be nothing less than perfect in order to take anything out of the match at the Mestalla.
Romeu is hoping to make his first start of the season for Los Che as they bid to bounce back in style from their disappointment last week.
Romeu said: "Barcelona are a strong opponent, if not the strongest, and we have to be prepared and in the right frame of mind to play well.
"You either have to play perfectly or you've got no chance. Hopefully we'll have a perfect game."