Although Reds fans understandably let their feelings be known about the club's debt and their American owners during the 4-0 home win against Hull City last Saturday, Fergie believes the derby and semi- final combination will get the support 100 per cent behind the goal of reaching Wembley.
"It will be different tonight because it is far more important now," he said.
"There is nothing wrong with supporters complaining. It is quite right. If the players play badly they are quite right to voice their disapproval. If they don't like the performance, they are quite right. If they don't like this or that it is their right. It is their club.
"But we don't want the divisive part in the club. We want the supporters behind the players all the time because we are coming to that part of the season where everything is down to what we do as a team.
"That's the most important thing, the team, always the team. We should never lose sight of that. Tonight we will see that. The fans will be fine.
"Everyone should be buckling down to makes sure we are successful, including the players, the staff and the supporters in particular.
"When they are in full voice it is great and we have had this experience at Old Trafford so many times over the years in big game situations, particular Wednesday nights.
"Some of the European nights here have been the most thrilling of my life. It is an incredible experience.
"The Barcelona, Juventus nights - you can't beat it. You all go away at the end of the night totally satisfied that you are at the right place at the right time in your lives.
"The supporters have shown great emotion towards players who have deserved it. Players who have made them do that, those who have made them get their backsides off their seats to cheer on a team who have produced unbelievable moments.
"Hopefully we can produce that tonight again. I can think of a number of big game situations going into a second leg knowing you have to win. We have played against some great teams over the years and you hope that experience helps us."
Source: Manchester Evening News