Keith Mason, who is one of the game's better-known players, was dismissed for gross misconduct last October after a picture of then Huddersfield Giants team-mate Scott Moore appeared on his Twitter account.
The picture, which was of Moore’s backside, stayed online for two days before it was removed.
Mason told the court his girlfriend had Tweeted the image from his mobile phone after a post-season drinking binge with team-mates.
The court heard that the photo was taken without Mason’s knowledge, and that his girlfriend had decided to Tweet it while looking through his phone.
The club decided that Mason, who is one of the sport’s highest earners, had broken their disciplinary code and that the Tweet was contrary to their "family values" and Mason’s status as a role model.
Prop Mason was at the Giants for seven years and had three more seasons to run on his contract.
Martin Budworth, representing Mason, said: "He has a considerable number of followers and the club believe the image could have been viewed by a considerable number of people."
Mason's lawyer added that his client felt the club had used the incident to get him off the payroll, as two players were brought in after his sacking – on a lower combined wage than his.
The court heard that Mason and his team-mates had drunk alcohol from Sunday to Tuesday after their final game of the season.
Mason insisted that the Tweet stayed online for 48 hours because he had been "worse for wear" and didn't realise his girlfriend had posted the picture.
"If I’d seen the tweet in the right frame of mind I would have taken it down straight away," he told the court. "I've never tweeted anything of this nature.
"There is no way ever I would leave a picture on my Twitter to offend anyone, especially someone's backside."
He added that he took it down once his hangover subsided, not because his attorney had advised him to.
"When I came round I took it off. I never thought at the time I would be getting a sacking two or three weeks later."
- Sports & Recreation