Koroisau was handed a grade-two dangerous contact charge by the NRL's match review committee on Friday for a first-half hip-drop tackle on Canberra's Noah Martin in the Tigers' 33-14 Thursday night win.
The hooker had escaped with paying $5800 in fines for charges already this year but his rap sheet has caught up with him and could leave him with no time to prove his credentials to Blues coach Laurie Daley.
Koroisau has not played Origin since 2023 but has been key to the Tigers' renaissance this season.
If he accepts the three-game suspension, Koroisau will miss the Tigers' next three games - away to Cronulla and Melbourne before a Magic Round clash with Manly in the weekend that doubles as a final Origin audition ahead of the Blues naming their squad for the series opener on May 27.
Assuming he pleads guilty, Koroisau would return for the Tigers' round-13 clash with Canterbury on May 30.
Koroisau risks an extra game on the sideline if he challenges the charge at the judiciary and loses.
The Tigers No.9 would escape with a fine if he successfully fights the charge.
Given his importance to the high-flying Tigers - and coach Benji Marshall's belief the hooker did nothing wrong - the club has until Saturday to decide if they will contest the grading in a bid to clear Koroisau to play.
Marshall hit out at the standard of officiating on Thursday night when the Tigers recorded their fifth win of the season.
"The inconsistency of the referees is annoying me at the moment to be honest," coach Marshall said.
"I know we won but some of the calls … it's hard to understand.
"In Api's case with the sin-bin, I don't know what he's supposed to do in that situation.
"He's making a cover tackle from behind, of course he's going to land on his legs.
"There's heaps of things that didn't go our way, I just think the fans deserve some consistency around the interpretations of the rules - and we're not getting it."
The Tigers outfought and outthought Canberra, who have won just three games all season and look a shadow of the team that claimed last year's minor premiership.
Halfback Adam Doueihi bagged two tries, kicked four goals and added a late field goal to push his case to be part of NSW's squad for the series opener on May 27.
Blues great Andrew Johns has pushed Doueihi's case because of the playmaker's versatility.
"It was his best game, impact wise, positioning, and where he played in the team," said Marshall, whose side face Cronulla and Melbourne over the next fortnight.
"Setting up everyone else and putting himself in the picture, kicking game, controlling the game.
"Andrew Johns is a pretty good judge of talent so if he's saying that, then yeah, put him in."
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