Moyes needs to man up and stick with 2 centre backs, week in and week out. That's the only way we're going to improve. CBs don't even run much in a match, so playing twice a week isn't an issue. If it's Jones and Evans then fine, go with those two. Vidic is suspended, Rio is off selling hats or something and Smalling can practice kicking against a wall until he works out how to play with a football.
The one thing, ONE thing we all expected from Moyes was that we'd be tough to beat. We're probably (literally) the easiest team in the league to play against right now. We don't pressure, we don't hold a line, we don't defend as a unit and we're vulnerable to 3 or 4 individual mistakes every match.