I think the new manager should be in on day 1, not waiting a fortnight. I don't know about anyone else but I've seen it many times in the real world that as soon as it is known that the current manager is no longer someone you have to impress or work hard for then people are on wind down. Like the run in to Xmas where not much gets done. Why would the players be working hard in training, learning new things etc when they know the work they are doing might be irrelevant in a week or two.