He showed great PRESENCE on the block not to throw a block into the defender's back when the defender was turned around. He set the screen and waited for the defender to turn back around before throwing the block. There are players that are not present enough to make that play in the moment and will throw that block into the defender's back. If he does that, no TD and more "cut Morgan" posts.
The replay of his block is at 48 seconds
RG3 76 Yard TD Run Against Vikings 10/14/2012 - YouTube