The superstar fullback's NRL season and Origin hopes are hanging by a thread after he underwent scans on his left shoulder on Saturday afternoon.
Manly expected to get the results on Saturday night or Sunday morning, however the course of action they take the length of his rehabilitation may not be decided so soon.
Trbojevic was hurt diving and jostling with Makahesi Makatoa for a loose ball as he attempted to prevent an Eels try in Manly's 22-20 loss on Friday night.
There remains some hope he could be able to return within two months, but there is greater concern his season may be almost over if the damage to the joint is serious.
His injury comes as a major blow not only to Manly but also NSW, with any chance of him playing in the State of Origin series-opener on June 8 seemingly gone.
Trbojevic and brother Jake cut disappointed figures after the match, with players doing their best to comfort the fullback amid his wretched run of injuries.
"He's not great," hooker Lachlan Croker said.
"It's hard to be positive when these things happen. It's tough one.
"The first thing he said to us was sorry. It's just the type of guy he is ... It almost makes you feel worse for him.
"He would be so upset (feeling) that he let us down and didn't finish that game with us. Fingers crossed (it's not bad)."
Manly players were clear Trbojevic had nothing to apologise for after they surrendered a 20-10 lead late.
Trbojevic's injury is also a blow for the NRL, given the 2021 Dally M Medal winner is one of the game's most exciting players.
Manly players are adamant they have learned to play without him, while also not blind to the fact they are a far better team with Trbojevic in it.
At one stage Manly had won just seven of 31 games without their fullback between 2019 and the opening month of 2021, but they have claimed victory in seven of nine since.
"It's never good," Croker said.
"Obviously the calibre of player he is. You can't help but think where that leaves him and where it leaves us with the extent of the injury."
Meanwhile Reuben Garrick said he now felt comfortable stepping into the fullback role from the wing, after doing so for a month earlier this season.
"The more you play in any position, the more you get a feel for it," Garrick said.
"Especially at the top level. You have to have all your numbers down pat. Otherwise the great playmakers will take advantage of it.
"I am feeling more comfortable with it."
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