Ferguson has warned Liverpool failure to qualify for the knockout stages of the Champions League will have a devastating effect on their Premier League prospects.
He explained: "It's difficult for them [Liverpool].
"It happened to us a few years ago when we went out at the group stages and did not even qualify for the UEFA Cup because we finished bottom of the table.
"We only scored three goals in the group and paid the price for that.
"When that happens you are naturally going to get criticised, but the most worrying thing is the effect it has on your players.
"It's a big disappointment they have to cope with and it can have an adverse effect for the rest of the season."