Joe Lewis insists team-mate Scott McKenna won’t repeat the mistake he made the last time Aberdeen played Rangers.
Centre-back McKenna was sent off for retaliation during the 4-2 Premiership defeat at Pittodrie last month.
The Scotland international kicked out at Rangers striker Alfredo Morelos after the Colombian – who was also sent off – had stamped on him.
McKenna is set to start today’s Scottish Cup quarter-final tie between the Reds and Gers at Pittodrie and Lewis says the defender won’t be affected by his dismissal.
The goalkeeper said: “Discipline can be important and it’s unlike Scott to act like he did in the last game.
“He put his hand up after the game and said he’d made a mistake.
“We move on because he is not a player who will do that again and I’m convinced of that.
“If Scott is back in the team he will be looking to make amends by making sure the defensive performance is very good.
“He’s a great guy, Scott. Psychologically, he is brilliant and he is laid-back.
“That one incident is very unlike him and I’m sure it won’t happen again.
“In terms of him maturing as a player, that will be a great lesson for him going forward.”
The Dons seem to bring the worst out in Gers striker Morelos who has been sent off on each of the three occasions he’s faced Aberdeen this season.
Despite his hot-headedness he is still a threat and has netted 27 goals in all competitions this term.
Two of those came at Pittodrie in the 4-2 win last month prior to his red card.
Lewis knows it’s important for the Dons to nullify his threat today.
He added: “He is an excellent player and they have a lot of very good players in their team after spending a lot of money.
“You expect a strong squad from them and they have strength in depth and quality whoever plays for them.
“Morelos has got quality, but we have to watch out for all of them.
“We have gifted away a few clean sheets this season and we would have liked to have had a few more.
“As a defensive unit it would be good if we could keep another clean sheet on Sunday.”