You can argue that it will hurt his confidence if he is dropped, and it's best to play through it, but for me, he is a professional player and part of a squad, and other players of equal standing are just as deserving of the position, and the chance to make it their own.
He could be having a spate of bad luck too, but jump back in the reserves and play out of it, and then await your chance again. Heitinga should get his chance now. I know sometimes Moyes plays Heitinga in the middle, but he must surely feel the position should be his now. It's not good for morale for players to never get picked, especially when you consider that Heitinga is a regular International, and Jags isn't.
Too many mistakes for me. Nothing personal Phil, but you can't keep making mistakes and keep your place. We have a squad.