Fa'asuamaleaui was placed on report for dangerous contact after his ball-carrying arm contacted Koroisau's face in the Titans' 28-12 win on Thursday night.
The Tigers and NSW rake was taken to hospital with a broken jaw and booked for surgery in Sydney on Friday.
Coach Tim Sheens confirmed his skipper would miss at least six weeks, including the remainder of NSW's Origin campaign.
A lock for selection in the second Origin game on June 21, Fa'asuamaleaui faced a nervous wait for the match review committee's charge sheet on Friday morning.
The 23-year-old was charged for a similar offence in round 12 when his forearm made high contact with Canterbury captain Reed Mahoney, but escaped suspension with a fine on that occasion.
The MRC declined to charge Fa'asuamaleaui on Friday morning, paving the way for him to line up in Game II, when the Maroons have the chance to close out the series.
The Titans skipper defended his technique while running with the ball.
He said he'd always adopted the same approach since joining the NRL, adding sometimes players "put their head in the wrong position".
"It is a contact sport," said Fa'asuamaleaui.
"I am running as hard as I can. He is getting up to try and stop me and came off second best. I am hoping he is alright.
"I think it is similar to the other week (after the Mahoney incident). It is just the media making me more worried than anything, just trying to build it up."
Analysing the Koroisau incident on Channel Nine after the game, Maroons assistant coach Cameron Smith said it was a different style of case to Fa'asuamaleaui's incident with Mahoney.
"Looking at the incident, I am trying to find what is illegal about the action," he said.
"If you actually see the bump which he makes on Api Koroisau, it is with his ball-carrying arm … his right arm.
"Whereas you look at the last time he was charged, a few weeks ago, and it was when he led with his left arm into Reed Mahoney.
"I don't know what he is meant to do with that ball-carrying arm. Is he meant to make it disappear?"
Fa'asuamaleaui believed fellow Titans prop Moeaki Fotuaika deserved to play his first game for Queensland since 2021 after another strong performance against the Tigers.
The Maroons are already without key forwards Jai Arrow (syndesmosis) and Tom Gilbert (shoulder surgery) for the rest of the series and Fotuaika is one of at least seven players in contention.
"I think he has been our best player mostly every week," Fa'asuamaleaui said.
"Obviously there have been some injuries and I am hoping his name is tossed up. He is the guy that does all the little stuff and works hard. I am hoping he gets picked in the team."
