Scans on Monday have confirmed a complete rupture of his anterior cruciate ligament in his left knee.
Moga will have surgery in the next few weeks and will be out for the rest of the 2018 season.
Following surgery, Moga will need to undergo an intensive rehabilitation program over the next nine to 12 months.
Tautau Moga injury; change of direction off left leg is where injury occurs. If confirmed would be 4th ACL injury for Moga (has had 3 in right leg already), 3rd in 24hours across the NRL (after Sironen & Tanginoa last night)#NRLDragonsKnights pic.twitter.com/NhKvtMtJKo
— NRL PHYSIO (@nrlphysio) April 1, 2018