Morelos received the club’s eighth red card of the season during the midweek defeat by Aberdeen - his third, although his first was later downgraded to a yellow card.
The Colombia international was already suspended for Sunday’s trip to Dundee and will now miss the visit of Hamilton, while Scott Arfield completes a two-match ban at Dens Park after he was sent off against Hearts last weekend.
Manager Steven Gerrard expressed his frustration on Wednesday night after Morelos received a second yellow card for lashing out at Graeme Shinnie with his arm, and Kyle Lafferty committed several fouls after being booked.
McAllister feels decision-making is the main issue and he believes talking through the problem, with Morelos especially, can help provide a solution.
But he warned the players they need to learn fast.
When asked if Rangers needed to address the issue, McAllister said: “Of course, there is a discipline problem with the number of red cards and bookings we have had. But it’s something we are working on continually.
“The players are working at it, we are trying to pass on years of experience to players that maybe haven’t been in these situations before. So everybody at the club is trying to improve the whole discipline issue.
“The communication between the management staff and playing staff is good. We are continually chatting over all sorts of issues. This is obviously one that is hitting the headlines at the moment. We are continually talking and that will not stop.”
Morelos had scored in Rangers’ seven previous Ladbrokes Premiership games before being sent off just after the hour mark in the 1-0 defeat against Aberdeen, and his absence leaves Kyle Lafferty as Gerrard’s only real attacking option.
“We will miss him, there’s no doubt about that,” McAllister said. “But it’s a learning process for him continually. He’s a very competitive guy, but we back him and we are sitting with him probably more than most, as you can imagine. We want to help the guy.
“Every time he misses a game, it’s an opportunity for him to score a goal, and he wants to score as many goals as he possibly can. Likewise, as a management staff, we need him in there because he’s our main threat.”
Former Liverpool team-mates Gerrard and McAllister are trying to press home the need for their players to retain cool heads in pressure situations.
“It is a fine line, there is no doubt about that,” the former Scotland captain said. “We’ve got loads of competitive players and generally, when you are on a yellow card, there’s got to be moments when you make split-second decisions. Sometimes we have made poor decisions.
“That’s what it is, it boils down to decision-making. When you are in the heat of the battle, you have got to still be thinking clear.
“We have players adapting to the refereeing and the style of play, but you have got to learn quickly.
“You have got to have steely determination, and that will to win should never disappear, but at times in games you have got to be cute as well.
“Playing a situation, playing a crowd, playing the referee. And that does come with experience, we have a lot of young players in the squad as well.”