I was watching Oher at practice today, saw him reaching out to block instead of using his feet and you captured this in a picture you took Jeremy, that's why he's getting beat. Probably learned bad habits trying to nurse that toe, easy to fix but may take some time while he builds the confidence to know that he can really kick slide without experiencing pain or re-injuring it.
In some ways tackle is easier than guard. It requires more athleticism but is less complicated in terms of blocking assignments. Silatolu struggles with stunts, blitz pickup, etc... so he would be less exposed mentally and more exposed physically.