'Major setback' for the English camp after Atkinson goes off with a hamstring injury.
The English seamer further complicated the fitness woes of the England squad when he left the playing area on the second morning in the Melbourne Test versus the Australians.
The pace bowler felt a problem in his left hamstring immediately following a delivery in his spell at the MCG.
The England team indicated Atkinson reported "discomfort" and required time off the field for further assessment "during the day".
The series decider in this Ashes battle at the SCG begins on Sunday, 4 January.
The visitors have already lost strike bowlers one seamer with a knee problem and another paceman to a side strain on the current trip.
Matthew Fisher was called up as injury reinforcement.
His form was underwhelming during the first two matches, taking just three wickets.
He was omitted from the previous Test, before being recalled for the Melbourne Test to fill the void.
Atkinson improved at the MCG, claiming a couple of wickets during the host's first knock, before adding 28 as a batsman among just a trio of English batsmen to reach double figures.
Post a single over in Australia's second innings, he returned the next day and removed Scott Boland taken by the wicketkeeper.
However, towards the conclusion of his spell, he sent down a slower ball to the batsman and promptly felt at his leg.
Gus Atkinson was recalled for the Boxing Day Test following his omission the Adelaide game.