Published: 14:00, 20 February 2016
Gillingham defender John Egan is out for six to eight weeks.
The central defender picked up a knock in training and is out with a knee injury.
Ryan Jackson also misses out for the Gills as he has not recovered from the recent knock he picked up in the match against Swindon.
It leaves the Gills well short in the defensive areas.
Utility-man Aaron Morris is to line up in central defence for the Gills at Oldham on Saturday.
Boss Justin Edinburgh is, however, hopeful of bringing in Deji Oshilaja next week.
A 93-day deal has already been agreed with the Championship side.
The Cardiff defender was on the bench for his parent club at the weekend and is expected to be in midweek as well.
But he is then expected to join up with the Gills in time to face Chesterfield next week.