Gilbert dislocated his shoulder during the first-half of Game 1 of Origin, and didn't return back to the field. Although, he did try and play on with the injury and even managed a tackle.
Set to undergo surgery, The Daily Telegraph reports that scans showed the injury was "worse than first feared".
Gilbert has been one of the better players for the Dolphins this season, since leaving the Cowboys. This included him being called-up for Queensland in the State of Origin squad.
It is more unfortunate news for the new expansion club, as Anthony Milford and Jarrod Wallace will miss the next three games due to suspension. Coming off a loss to the Warriors, the duo were both charged by the MRC for dangerous tackles.
It is unknown who Wayne Bennett will call-up in the absence of the three players, however, he will have an extra player to choose from next week.
Enforcer Felise Kaufusi won't be available against Manly this week, but will return in their following home and away game as he is still serving suspension for a dangerous tackle against the Storm.