The Canaries face three games in eight days that will decide their Premier League future, playing United and Watford at home and Everton away.
And Neil said : “It’s certainly the most important eight days of my career as a manager and United is the biggest game of all our lives.
“Our recent home game against Sunderland was big but this one is even bigger because there is so much riding on it.
“I have had a lot of important games before as a player and as a manager, many of them involving promotion and relegation.
“But this one game has more riding on it than any I have ever known before. It’s not win or bust – but it’s absolutely crucial.”