The Tongan international was initially ruled out for the season when picking up a bicep injury in the home win over Huddersfield in July, but had hoped to return ahead of schedule to provide a welcome boost for the Airlie Birds during the play-offs.
But after seeing a specialist regarding his injury last week, the barnstorming forward has now been told he will not pull on the Black and White again before leaving to join Sydney Roosters in the NRL next season.
Gentle said: “The report that Sam got back from the specialist last week wasn’t terrific, we’ve spoken to him about it and decided he won’t be back for us again this year. Sadly, Sam has played his last game for Hull FC.”
“The 17 who played last week have all come through the game and it’s probably a bit late to be bringing players into the side now.
Moa opted to return home to Australia to be closer to his partner and family, and leaves the Black and Whites having made 78 appearances for the club, scoring seven tries.
He said: “It really hit me that I’m actually leaving when everybody paraded around the pitch after the Castleford game. It sunk in then that I might not get to play for the club again and I got a bit emotional.
“From my point of view, I don’t want to be selfish and try to have one last hoorah if it’s not the best option for the team. If I don’t get to play, I’ll be on the side lines wishing my mates and the team the best.”