The star half was caught in heavy contact during his last game - which came back in Round 14 against the Melbourne Storm.
He lasted just half an hour before being taken from the field, then missed the Round 15 loss to the Parramatta Eels away from home leading into the NRL's representative round break.
It means Keary has already had two weeks off, and that will be extended to four weeks by the time he returns - or is next a chance at returning - with the Roosters to enjoy their bye ahead of the State of Origin decider in Brisbane.
The Roosters have been one of the season's major disappointments thus far, and with the club battling for a spot in the top eight after originally being forecast to be among the premiership favourites, halves combination Sam Walker and Keary have come under intense scrutiny for their own performances.
Manu's move to the halves is likely to see Paul Momirovski earn a reprieve and be recalled to the matchday 17 to take on the Panthers in what will be the ultimate test for the tri-colours.
The news regarding Keary comes though as Fox Sports report the Roosters will leave no expense on the table as they look to ensure Keary passes every medical test to return.
Given his injury - and concussion in particular - history though, it's reported that medical retirement could ultimately be an option on the table, with the veteran half of 171 NRL games on contract with the Bondi-based club until the end of 2024.
There has been no indication from the club yet that they may steer that way, however, Keary's recovery will ultimately determine his future in the game.