"A goalkeeper who is sent off must be replaced by an eligible player." IFAB Laws of the Game 2016-17, p74.
An eligible player is defined as someone who finished the game and is listed as one of the penalty takers.
I know about the fabled 'Law 18', and my argument on Twitter isn't about whether he should have order a re-take. To my mind, he shouldn't have - not without there being a clarification of what 'moving off the line' means in reality.
What's going on on Twitter is a Man U fan who believes the ref...
Well, he clearly wasn't miles off his line. As was pointed out, one foot was still on the line.
The issue, unfortunately, is back to our old mucker '... but what about...?' The keeper's position when the shot was taken was no worse (in terms of being off his line) than many, if not most...