Rotherham are waiting on the results of a scan on Kari Arnason's injured shoulder.
The influential midfielder suffered the problem during Tuesday's 1-1 draw with Fleetwood and - after suffering bruising to his joint - looks set to miss Saturday's clash at Dagenham.
Arnason has undergone a precautionary scan and the Millers are awaiting the results to determine the likely length of the Iceland international's absence.
"We are waiting on the result of the scan, but he is very doubtful for Saturday," boss Steve Evans said.
"It could be a couple of weeks, we just don't know.
"It is pretty sore, he fell on the hard ground. It's not dislocated, we know that.
"It weakens us when he is not there, but he is the best player outside the Championship, he's at that level. So, of course we will miss him, but it is about opportunities for other players."