Schuster was named to come off the bench on Saturday afternoon, but the club made a late decision to rest him from the game.
In a statement, the Sea Eagles said Schuster was being "saved" for next Saturday's pre-season match against Brisbane.
Manly fly out for Las Vegas on Wednesday, before the Broncos trial.
But Manly officials insist there is still potential for Schuster to fly to Las Vegas next Sunday, and have a week in the US before the season opener against South Sydney there on March 2.
Schuster has endured a difficult off-season, including suffering from chickenpox before Christmas.
More recently, a calf injury has restricted his training.
The 21-year-old was able to get through the last week of training unscathed, but Manly still opted to leave him on ice in Gosford.
One of the most talented players in the NRL, Schuster is making a full-time switch back to the second-row this year after an injury-plagued season at five-eighth.
But he faces a battle to claim a starting spot, with Ben Trbojevic a chance to claim the left second-row spot at the Sea Eagles.
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