Probable starting eleven:

Barcelona:
Valdes, Puyol, Pique, Abidal, Adriano, Fabregas, Busquets, Iniesta, Sanchez, Messi, Pedro

Valencia:
Guaita, Miguel, Rami, Dealbert, Mathieu, Albelda, Banega, Feghouli, Jonas, Piatti, Soldado

Barcelona is the best team in the World, but I see chance for Valencia to stay unbeaten at Nou camp. The first reason is psychological. Real madrid have big advantage (13 points at the moment) and it is clear Barcelona have slim chances to defend the title. It will be very hard for Barcelona players to find proper motivation. Plus, the key midfielder Xavi has a calf injury and most probably won't play. That's not all, Javier Mascherano and Dani Alves are both suspended. Ibrahim Afellay and David Villa are still out. Valencia on other side is not a naive opponent, they are on the third place and they are excellent team. Last weekend they won 4:0 against Sporting Gijon, while at Thursday won 1:0 against Stoke in UEFA Europe League. Even more, that victory was obtained on road.

This is gonna be the third match between Barcelona and Valencia this season. In September they played 2:2 at Mestalla in Primera. Then they met twice in Copa del Rey. The first match ended 1:1, while Barcelona won 2:0 the reverse fixture and managed to qualify. So, Valencia already played two draws with Barcelona and I believe they are able to repeat that once more.