Valverde had voiced his concern ahead of the game with the pitch recently relaid.
"The state of the pitch has played a big part in the match," he said after seeing Ousmane Dembele score Barca's winner.
"I am not saying that there were not other elements also with Valladolid playing their part but the playes slipped, the pitch came up and we had some injuries.
"The truth is that it seems incredible in this day and age it can happen like this. I imagine that Valladolid did all they could and there will have been a reason why the pitch was not put down before. "
Dembele scored the only goal of the game and for the second match played an important role.
"We tried out different tactics and as the game went on Leo (Messi) came inside and we made the change," added Valverde.
"As the game went on Valladolid caused us some problems."