Seamer Gus Atkinson Adds to England's Fitness Worries.
'Significant concern' for the touring side after Atkinson is forced off suffering a hamstring problem.
The pace bowler further complicated England's injury problems upon exiting the playing area during Saturday's play of the Boxing Day Test versus the Australians.
Atkinson experienced discomfort in his hamstring immediately following a delivery that he bowled at the MCG.
The England team indicated the 27-year-old reported "discomfort" and would spend time on the sidelines for further assessment "in the coming hours".
The series decider in this Ashes battle in Sydney gets underway on Sunday, 4 January.
The visitors have already lost strike bowlers Mark Wood with a knee problem and Jofra Archer with an abdominal strain on this Ashes tour.
Matthew Fisher was brought into the squad as injury reinforcement.
His form was underwhelming early in the series, taking just a handful of scalps.
He was left out of the third Test, before being recalled for the Boxing Day match in the playing XI.
The county bowler improved at the MCG, taking two wickets during the host's first knock, then making 28 with the bat as one of just three English batsmen to reach double figures.
Following a brief spell late on the first day, he returned on Saturday morning and removed Scott Boland taken by the wicketkeeper.
However, on the final ball of that over, he bowled a slower ball to Travis Head and suddenly grabbed at his leg.
The English bowler was recalled for the Melbourne match having missed of the third.
