Rangers striker Morelos was sent off for a third time against the Dons this season when he and McKenna were both sent packing for kicking out at each other in the Ibrox side’s 4-2 win at Pittodrie last month.
The Colombian’s first red card, which was later rescinded, came after he booted McKenna when the Aberdeen and Scotland centre-back barged him in the first game of the Ladbrokes Premiership season.
The latest instalment in their running feud comes tomorrow afternoon when the teams meet in the William Hill Scottish Cup quarter-finals.
Gerrard claims he does not need to warn Morelos to temper his behaviour as he relishes another physical duel.
The Rangers boss hopes that both players manage to stay just on the right side of the laws of the game.
“I think they are both box office to watch for neutral people,” Gerrard said.
“I’m sure it will be another physical battle between them and hopefully both players stay on the right side this time and we can see that box-office battle for 90 minutes, because I think it was a real shame both of them getting sent off last time. I was really enjoying it. Scott’s a tremendous defender, he’s always physical, and Alfredo on the day was unplayable.
“It was certainly great to watch but hopefully both players can stay on the pitch for 90 minutes this time because they are the type of players and battles that everyone wants to see, but not for just part of the game, but all of it.”
Morelos scored two goals at Pittodrie last time out and has now netted 28 times this season despite missing six matches through suspension.
Gerrard, pictured, warned after his latest red card that Morelos needed to channel his aggression in order to reach the next level of his game.
But the former Liverpool captain would not heap any added pressure on his talisman ahead of this particular fixture.
“Alfredo doesn’t have to prove anything to anybody but himself, and that’s just to go out and give us the best performance he has got,” he said. “The goals he scored up there were top class and his all-round performance was unplayable.
“A lot of defenders have to be physical with him to try to stop him. But Alfredo should see that as a compliment.
“He just needs to focus on the game and what we need him to do to try to help us get an important win.”
Gerrard expects a physical encounter all over the pitch.
“We know Aberdeen are going to be fired up for it and these games are always very tense games with a lot of physicality in the games,” he said.
“The players are well aware of that but I think the players are really looking forward to this. It is a huge game for us and it is a competition we want to do really well in, so we can’t wait for it to start.
“Every test we have had against Aberdeen this season, whether it be win, loss or draw, has been very physical and they have all been really good spectacles.”