A six-week lay-off would mean Trbojevic, who has a long history of hamstring issues, could return for Manly's first game after the State of Origin series opener.
But the 10-time NSW representative would miss both that game and Origin II, returning for round 16, if he required the full eight weeks on the sidelines.
Trbojevic would have been in contention for a spot in NSW's outside backs given a good start to the season at the Sea Eagles, but now faces the prospect of missing a third consecutive series.
The 29-year-old suffered a moderate hamstring injury in his left leg in the first half of Manly's big win over North Queensland on Thursday night.
Trbojevic cut a devastated figure as he left the field in Townsville, his latest hamstring injury believed to have been the eighth he has suffered in the past eight seasons.
The luckless former Dally M Medallist now appears likely to go an eighth consecutive year without playing more than 20 games in a season.
Tolu Koula is a ready-made fullback replacement for the coming weeks, when Manly's resurgence under interim coach Kieran Foran will be tested.
Clayton Faulalo is the likeliest man to slot into the centres, as he did in Thursday's win, Manly's third from as many matches since Foran took over.
The Sea Eagles face Parramatta next Sunday for their first home game since Anthony Seibold was axed as coach three games into the season.
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