The former Scotland international prevented a throw-in from being taken in injury-time which resulted in the second yellow card - and a one-match ban.
McLeish said: "Ferguson is out through suspension which will be a loss to us because of his ability to make us play and we will have to try and patch things up.
"I think by and large the discipline of the side has been good. It was a rash moment and Barry admits that.
"You have to keep talking to the players every week in the team talks and I've reminded them every single game about discipline and the need to keep all the players on the pitch, to try and avoid the bookings.
"It is a man's game and sometimes tackles earn you bookings. It's the silly ones we've got to try and cut out, pulling the jersey over the head when we score a goal.
"We have to watch the discipline because we are a small, fragile squad and it will affect small squads."
McLeish is under no illusions as to the task facing his side against the Reds despite them registering only one win in their last eight games.
And the former Scotland boss believes they will take encouragement from the 1-1 draw in Lyon in midweek despite a late equaliser leaving their Champions League campaign in the balance.
He said: "Monday is a different game as opposed to the Lyon game but I am sure Liverpool can take a lot of pleasure out of their performance.
"I am sure the manager will be pleased with the overall show on the night. Lyon huffed and puffed but Liverpool had the better of the game.
"It is galling to lose the three points the way they did and a severe blow and a dent sometimes to the confidence.
"But the players will be aware they played a whole lot better than at Fulham and the league campaign is totally different anyway.
"It's at Anfield, they have a pretty good record there, they won their last game there against the champions (Manchester United) so we are under no illusions about how tough a task it is."
Birmingham's on-loan Manchester City keeper Joe Hart is available after being ineligible to face his parent club although his deputy, Maik Taylor, impressed against Mark Hughes' side.
Winger Keith Fahey is battling to overcome a knock to his knee in training but striker Garry O'Connor is still troubled by a groin problem.