Hull FC coach Richard Agar has been fined £6,000 following his outspoken criticism of referee James Child.
He was found guilty of breaching the Rugby Football League's operational rules and respect policy for his comments after losing to Castleford.
Agar described Child's performance as "disgraceful", accusing him of completely ruining the game.
And he has been fined £3,000, payable immediately, with a further £3,000 suspended until the end of the season.
After the match at the KC Stadium on 1 April, which Hull lost 20-18, Agar said: "I'm angry. I saw this bloke referee a trial game between Salford and Hull KR and I thought: 'I'm dreading when we get him'.
"Sure enough he's backed it up. Just a disgraceful performance. I've got seasoned Test players in there coming in shaking their heads in disbelief.
"It's just been a good game and a good spectacle punctuated by ridiculous decisions, completely ruined by one bloke."
After the April Fools' Day home defeat, Hull were 11th in Super League, just four points off the bottom, with just two wins from their first eight matches.
But they have since lost just once in five matches to climb into the play-off places.