Ferguson has praised manager Paul Lambert for the job he is doing with the Canaries.
United face Norwich at Carrow Road on Sunday.
“It is difficult to say who is going to go down,” Ferguson said.
“When you look at the bottom of the league, there are five teams from 19 to 21 points. There is not a great deal of leeway there.
“But 21 to 35 is a big gap and I think Norwich are okay.
“They look as if they are enjoying themselves and it is always a good atmosphere at Carrow Road. They get a full house every game.”
“I knew Paul Lambert as a kid at St Mirren,” added the United boss.
“He played under my brother Martin when he was a coach there.
“He had a great career, winning a European Cup winners medal with Dortmund, then going to Celtic.”
