Ellis hobbled from the field shortly before half time during the Tigers’ golden point reverse at Allianz Stadium and underwent scans yesterday.
The results were not good for the Hull-bound second rower, with doctors ruling him out for between two and three months,
Ellis will see a specialist tomorrow and could yet have surgery on the injury.
Meanwhile, prop Keith Galloway could make a surprise return for the Tigers when they take on Brisbane on Friday night.
Galloway suffered damaged foot ligaments in the opening round victory against Cronulla but will require tests to determine his availability.