Paceman Atkinson Adds to the English team's Injury Problems.
'Significant concern' for the touring side after Atkinson leaves the field due to a hamstring issue.
The English seamer further complicated England's injury problems after leaving the field during Saturday's play of the Boxing Day Test against Australia.
Atkinson experienced discomfort in his hamstring immediately following a delivery in his spell on Saturday.
Team management indicated the 27-year-old had experienced "tightness" and was to take time on the sidelines to undergo evaluation "during the day".
The concluding match in this Ashes battle at the SCG starts on Sunday, 4 January.
The visitors have previously lost key quicks Mark Wood with a knee problem and another paceman with an abdominal strain on the current trip.
Matthew Fisher was added to the party as cover for Wood.
The seamer had a tough time in the opening two Tests, taking just a handful of scalps.
He was left out from the previous Test, then recalled for the Melbourne Test as Archer's replacement.
Surrey's Atkinson improved at the MCG, bagging two scalps during the host's first knock, then making 28 while batting being one of only three English batsmen to reach double figures.
Following a brief spell at the end of day one, he came back for the second day's play and removed Scott Boland Scott Boland caught behind.
Unfortunately, on the final ball of that over, he sent down a slower ball to Travis Head and promptly felt his left hamstring.
Gus Atkinson was brought back for the Boxing Day Test after being left out the previous Test.
