The Dolphins now have eight of their top 30 squad absent with long-term injuries after scans on in-form playmaker Kodi Nikorima's hamstring.
Nikorima is predicted to miss six weeks and is due to return in either round 23 or 24 after suffering the injury in the 38th minute of the 50-28 win over South Sydney.
The club already has key forwards Max Plath (knee), Tom Gilbert (shoulder), Daniel Saifiti (shoulder) and Thomas Flegler (shoulder) out for the rest of the year.
Veteran forward Felise Kaufusi is due back from a medial cruciate ligament (MCL) injury in round 22, as is recent prop signing Sebastian Su'a who joined the club from Newcastle with a lingering knee issue but is yet to play a game.
Winger Jack Bostock is also out of action until next year with a season-ending anterior cruciate ligament (ACL) injury.
With the Dolphins having byes this weekend and in round 21 Nikorima, who has been in lethal form, may only miss three or four matches.
The Dolphins are in eighth position and will likely need to win four of their remaining eight games to reach the finals if 30 competition points is the cut-off for the top eight.
They at least have the advantage of a for-and-against of plus-162 - the second best behind Melbourne.
Dolphins coach Kristian Woolf does have options to replace Nikorima ahead of the round 19 away clash with Cronulla on Friday week.
Utility Kurt Donoghoe, who played in the halves for Fiji in last year's Pacific Championships, is one possibility. They could also move Jake Averillo from centre to No.6 or bring in natural half Sean O'Sullivan.
While Donoghoe has been one of the side's best performers in multiple positions this year and is the obvious replacement, the loss of Nikorima is a blow.
His liaison with Katoa has been instrumental in the Dolphins' surge into the top eight.
The duo are recognised as one of the leading pairings in the NRL this year, their creativity and close understanding integral to the side's attacking strength.