However Cahill was set to appear for the second half of yesterday's 2-0 defeat at Scunthorpe but tweaked his knee in the half time warm up.
MillersMAD is unsure of the length of the absence but will keep you updated with all the squad news as and when we have it.
Danny Harrison had to miss Saturday's trip to Stockport as his wife went into labour, and is not injured contrary to terrace rumours, but boss Mark Robins still hopes to seal a deal for another player before next Friday's transfer deadline.
The boss would still be able to bring in loanees after the deadline has passed, but the recent departures of Craig Fleming and Pablo Mills, who's joined Crawley Town for a month, could mean a longer stay in South Yorkshire for midfielder Marcus Bean.