Ben Flower's shocking punch on Lance Hohaia overshadowed St Helens' crowning as Super League champions for a sixth time after beating 12-man Wigan 14-6 at Old Trafford.
Flower was dismissed after just two minutes after knocking Hohaia to the floor before punching the New Zealand back.
Referee Phil Bentham consulted with the video officials before showing Flower, 26, the first red card in Grand Final history.
Wigan took a surprise 6-2 half-time lead through Joe Burgess' try as St Helens struggled to assert their numerical advantage.
However, the 2014 league leaders eventually outlasted their opponents with Sia Soilola and Tommy Makinson securing Saints' first title since 2006.
However, the incident involving Flower has dominated the post-match debate with the Welsh international subject to swathes of criticism on social media.
Wigan coach Shaun Wane said: "It's a huge error today and we just move on. I make mistakes and he's made one today.
"You can't [defend it]. It's a rush of blood. It's the Wigan-Saints derby and everybody is getting whacked off the ball and he made an error.
"He'll be really upset with what he's done to his teammates, but that's just the character and why we love Ben Flower so much.
"The RFL will deal with the punishment accordingly, and whatever he gets, I'll stand by him. I'll make sure he understands that sort of thing can't happen again."
Flower faces a four- to eight-game suspension, however the ban could be extended if the incident is deemed to be serious.