That "one shocker" was one of the worst of his performances but the rest were far from acceptable.
He put in a shift for the team playing in that position and fair play to him for that - and yes, he had some good performances at the start of the season (all of which playing in midfield). I think he had and possibly still has a value within the squad as he's a useful squad player.
However I stand by him being awful in all of his left back performances with the exception of one or two games (or moments - e.g. the header off the line in the semi final).