The Millers already had a drama on their hands after strikers Kyle Vassell and Jamie Proctor joined long-term absentees Sean Raggett and Clark Robertson in the treatment room.
All four of those will be missing against the Robins along with a key man in the team, whose identity boss Paul Warne chose not to reveal.
'I have got another injury crisis, I have got a big player missing whose name I don't want to say,' Warne said.
'Initially we thought it was serious, but hopefully that player will be available for the weekend.
'He got scanned, he won't be available for Wednesday for sure. It's a blow for us and you'll see it's a blow when you see the teamsheet but that's the way it is.'
That disappointment is offset by skipper Richard Wood's likely fitness as the groin injury which saw him limp off against Stoke will not keep him out of the AESSEAL New York Stadium clash, while Michael Smith, the only remaining senior striker, is playing through the pain barrier.
To make matters wholly worse for the Millers, Zak Vyner is unavailable against his parent club.
Warne added: "It is a little bit of a crisis to be honest, if you go in our treatment room there is a lot of senior pros in there. They are big players for us, it is a bit of a problem.
'As long as I have got 11 fit I am happy. I have got a great team I can put out.'
Despite such an overflowing treatment room, Warne is not looking to supplement his squad with the signing of free agents.
'I don't think there is anything out there that will improve my squad,' he insisted.
'We run a pretty tight ship, I don't have a massive squad for many reasons.
'The fact that of my three strikers two and half of them are injured is not ideal.
'There are options in the free market but there isn't anyone who I think is suitable or will help us. If it means I have to play a round peg in a square hole I will.Â After the international break we should have everyone back.'