I don't think CB position has that luxury. It's the last defender that you can't keep making mistake, being switched off game after game to play into form. Most CB does well (and needs to) in term of form without a run of game. Bad CB make mistake and will always, while good one with improve further with experience. When we're talking about letting someone to get away with mistake, in hope that he may be just decent, then we're in trouble.I always think he is a player than needs to play all the time to get any kind of rhythm. The more unbroken game time the fewer the big errors. But He has had his chance now time to upgrade.
And what makes matters worse is that Sanchez can't even play fullback position even if he just needs game time to get on rhythm