Also, since the effect reads "1 creature within 5 feet of you" (similar wording to grease, cure light wounds, healing word, etc.), during my playtest I ruled that the knight could use his shield reaction to protect himself instead of an ally if he wanted. It was cool and seemed balanced. A goblin would go to throw a spear at him, but he raised his shield to block it (why shouldn't his shield training be able to protect himself as well as allies anyways, though I am not sure if this is their intent). Note while he almost always blocked the first blow, subsequent attacks against him would not have that disadvantage as he is distracted with the first guy.