Bradley came off in Tuesdays JPT game with York City and has suffered a hamstring injury.
However Nicky Hunt and Dale Tonge are both in contention to replace Bradley at right back after featuring in the reserves at Gateshead. New signing Craig Morgan could also be involved with Kari Arnason away on International duty.
Boss Steve Evans told Millersplayer: “Tongey and Hunty came through 65 minutes and both were excellent. Their fitness levels were both good and there were no issues this morning. Craig Morgan also played 45 minutes as planned so the squad is getting a little bit stronger day-by-day."
Evans added a few further thoughts on BBC Radio Sheffield: "Everyone knows we should have beaten Northampton but we took it on the chin and I think we should have won at Chesterfield too.
"Off the pitch it's carnage at Port Vale and I feel sorry for Micky Adams. They've got a good team though and I think Ashley Vincent and Tom Pope are excellent strikers and they're a handful for any defence.
"If we win on Saturday then we'll be averaging two points a game and if you do that all season then you end up being champions."
Millers fans can pay on the day using cash only as Vale are still in administration.