Rotherham utility-man Mark Bradley is set for a month on the sidelines with a hamstring injury.
The 24-year-old makeshift right-back suffered the problem during Tuesday night's 1-0 defeat to York in the Johnstone's Paint Trophy and will now be out until October.
"He will be out for four weeks. It's disappointing because he's been great for us," boss Steve Evans said.
"He's a great professional and we'll miss him. He can play lot of positions and that's why we kept him."
Bradley's injury has been off-set by the return of regular right-backs Nicky Hunt (hamstring) and Dale Tonge (Achilles), who both had a run-out for the reserves on Wednesday.