Mitchell Brown, Sean Wainui and Marty McKenzie were also under injury clouds after sustaining head knocks.
While Cooper said Brown was showing no signs of symptoms, the trio were all under the competition's concussion protocols and would continue to be evaluated.
"It's been an effect, no doubt, but a lot of confidence in the depth we've got and the group we have that we can bring others through," Cooper said.
On the topic of head knocks, Cooper addressed the tackle that saw forward Lachlan Boshier receive a yellow card, saying common sense should apply in that situation.
Boshier conceded a penalty try and was shown a yellow card in making contact with Ryan Crotty's head when the Crusaders' midfielder dove low for the try line.
"The law says leave the head alone, but there's got to be a common sense question around it. When you're diving so low, two players going so low, again do you let him score the try and not give the penalty, not give the yellow card away.
"I just think there has to be a common sense clause. Yes you've got to look after the players and you've got to look after the head, I agree with all that, it's just a common sense approach.
"You've got to get lower, and I don't know if they can get any lower," Cooper said when asked what a defender could do in that situation. "I guess that's where the common sense part comes in."
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