In the photos below we will try to portray the problem, but you will get a better idea if you look out for the YouTube highlights when they become available...
Example one. As the shot comes in from the edge of the box Moxey stops running, stops anticipating. He assumes that either the ball will go in or over the bar - he believes in his assumption strongly enough that he thinks it is ok to stop defending. It is NEVER ok to stop defending until the ball is "safe". A defender at this level should always, ALWAYS, be anticipating the unexpected - in this case he should anticipate that his keeper will make the save and there may be some clearing up to do. He doesn't anticipate the save and it leads to a goal! No wonder Amos is furious after such a great attempt at a save - he is right to expect more commitment from his defenders. This isn't the only time Moxey switched off too early either (see below).
This has nothing to do with ability! It all comes down to mentality! Ben Amos is a key player when it comes to mentality and you can clearly see his Manchester United ethos is ingrained within him. There is something slack about the effort of too many Wanderers players and they need to buck up their ideas. Fast!