Goals from Luiz Suarez (3), Philippe Coutinho (1) and Arturo Vidal (1) ensured victory for the Catalan club at the Camp Nou.
Marcelo’s lone strike was not enough to get a point for the visitors.
Valdano said Bale was the player in charge of marking Barca’s Jordi Alba but the Welshman lost concentration and the hosts got their first goal.
“We keep looking at Bale because of his price tag and that has created this illusion that he’s some sort of world superstar,” Valdano told Spanish radio station, Onda Cero.
“But the last five years aren’t reflective of what Real Madrid paid for him.
“Bale was the one in charge of tracking Jordi Alba (for FC Barcelona’s first goal), but after seven minutes his concentration was gone. Alba was on his own down that flank.
“At the start of the game, the players respected the system and their instructions, but then they do what comes naturally to them, like Bale did.
“They think they have the authority to do whatever they like and that can go against the collective.”