Fast bowler Atkinson Compounds the English team's Fitness Problems.
'Significant concern' for the touring side as Atkinson leaves the field with a hamstring injury.
Gus Atkinson increased the injury concerns plaguing England when he left the playing area during Saturday's play of the Boxing Day Test in the Ashes series.
The right-arm seamer experienced discomfort in his left leg post-delivery in his spell on Saturday.
The touring camp indicated the 27-year-old had experienced "tightness" and required time on the sidelines in order to be assessed "during the day".
The series decider in this Ashes battle at the SCG starts this coming Sunday.
England have previously lost fast 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 in the opening two Tests, claiming a mere a handful of scalps.
He was dropped of the third Test, then recalled for the Boxing Day match in the playing XI.
Surrey's Atkinson performed better in the fourth Test, claiming a couple of wickets during the host's first knock, and scoring 28 runs while batting as one of just three teammates to get into double digits.
Following a brief spell in Australia's second innings, he returned the next day and had nightwatchman Scott Boland caught behind.
However, towards the conclusion of his spell, he bowled a slower ball to the batsman and promptly felt for his hamstring.
Atkinson returned to the side for the fourth Ashes Test following his omission the previous Test.
