Rotherham defender Johnny Mullins was forced off in the draw at Macclesfield with an injury boss Andy Scott has yet to identify.
The 26-year-old was replaced in the second half at Moss Rose suffering from visual problems and Scott has revealed that the former Stockport man was unable to recall the cause of the injury.
"Johnny Mullins can't remember anything," Scott told Rotherham's official website. "We don't know what happened to him.
"At half-time there was no sign that there was a problem, then he went down and just said he couldn't see anything and can't remember anything.
"He just felt that the game was going two or three times the speed it was."
Substitute Troy Brown could fill in for Friday's game at Cheltenham if Mullins fails to recover in time.