Hardaker wrote on Twitter that he “can’t wait for Saturday” at 7.30pm on Wednesday night.
But the next morning he was told he would not be in the squad to face Leeds Rhinos due to a “a breach of club rules”.
It prompted the tweet to go viral with hundreds of retweets and some mocking responses from fans.
One replied “awkward” while another joked “where you get your ticket?”
Another posted four crying with laughter emojis and said: “Unlucky Zak.”
A fellow fan added: “I’d probs delete this.”
The in-form 25-year-old – this week named runner-up to Tigers team-mate Luke Gale for the 2017 Steve Prescott Man of Steel award – has been omitted from the squad for Saturday’s Betfred Super League showpiece.
The club have not elaborated beyond a short statement but taking such drastic action two days before the biggest game in their 91-year history clearly indicates how seriously they regard the matter.
The statement read: “Zak Hardaker is unavailable for selection due to a breach of club rules.
“The club will make no further comment at this point as full attention is focused on Saturday’s Grand Final.”
The Rugby Football League and representatives for the player have also not commented.
As well as disrupting Castleford’s Grand Final plans, Hardaker’s World Cup hopes could also be in jeopardy. England coach Wayne Bennett was due to name his squad for the upcoming tournament in Australasia on Monday.
Hardaker had enjoyed a fine campaign after joining the Tigers from Saturday’s Old Trafford opponents Leeds.
He was initially signed on a season-long loan but that was turned into a permanent deal, with Hardaker agreeing a four-and-a-half year contract, in June.
Although the player is no stranger to controversy.
He was axed from the England squad during the 2013 World Cup due to a breach of discipline which also earned him a final warning from Leeds.
Hardaker got his career back on track, helping the Rhinos complete the domestic treble in 2015 and winning the Man of Steel award, while he was full-back for England in their Test series triumph over New Zealand.
He suffered a loss of form the following season, which he put down to personal issues, and finished the campaign on loan to Australian club Penrith Panthers before being thrown a lifeline by Castleford.
His return to form earned him a recall for England’s mid-season Test match against Samoa in Sydney but now his international position is in doubt.