Paceman Gus Atkinson Adds to the English team's Fitness Concerns.
'Major setback' for England after Atkinson goes off due to a hamstring issue.
The pace bowler increased the injury concerns plaguing England when he left the playing area on the second morning of the Boxing Day Test against Australia.
The right-arm seamer experienced discomfort in his hamstring after the final ball in his spell during the morning session.
The touring camp stated the 27-year-old felt some "soreness" and would spend time on the sidelines for further assessment "during the day".
The series decider of the tour at the SCG begins on Sunday, 4 January.
England have previously lost fast bowlers Mark Wood to a knee injury and another paceman with an abdominal strain on the current trip.
Matthew Fisher was brought into the squad to provide backup.
The seamer had a tough time in the opening two Tests, claiming a mere a handful of scalps.
He was dropped from the previous Test, before being recalled for the Melbourne Test in the playing XI.
The county bowler performed better in the fourth Test, taking two wickets with the ball, and scoring 28 runs with the bat being one of only three England players to get into double digits.
Post a single over in Australia's second innings, he returned on Saturday morning and dismissed the nightwatchman edging to the keeper.
However, at the end of the fifth over, he sent down a slower ball to the batsman and promptly felt his left hamstring.
Gus Atkinson returned to the side for the fourth Ashes Test after being left out the previous Test.
