I don't think he is that prone to brain farts, the problem with him is that he is more of an old school fullback, pretty much the same as Shaw. They can't really fullfill neither of the two ways modern fullbacks or wingbacks are used. His passing and on the ball ability isn't good enough to tug in and play the fullback role that morphs into a defensive midfielder he also can't play the attacking fullback that provides width in the final third of the pitch and runs up and down the flank like a mad man. In short, he is just a very limited player in what he does well. I also have a particular dislike for the way he sometimes just dozes of in games seems to be not present on the pitch under Carrick that has almost completely vanished so it might very well be a confidence thing. He isn't a shit player, far from it but he also isn't a game changer. I feel like he is the type of squad player we used to have even under SAF. A fullback you can bring in if the main thing you are looking for is defensive stability or in the games against the big teams that offer you counter attacking possibilities but not the type of player you play when you are up against an underdog that plays a deep block.