The 32-year-old returned to the side earlier this month after an August op, but lasted only three matches before breaking down again and was ruled out of Saturday’s 4-0 defeat at Championship pace-setters Newcastle United.
“His back has problems,” revealed caretaker manager Paul Warne, who has lost out in his bid to sign Leeds United midfielder Toumani Diagouraga on loan. “Unfortunately, he’s going to have to have an operation.
“I think his season is done.”
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The absence of Broadfoot, who signed a new two-year contract last summer, is a huge blow for the bottom-placed Millers as they look to bridge a nine-point gap between them and safety.
“I am licking my wounds a bit,” Warne said. “I am trying my best to get the best out of this group.
“Broady is good in the dressing room, he is good on the pitch. At 2-0 down, he wouldn’t have accepted people not wanting the ball.
“I love him like a son. Every club has injuries and suspensions, but he is a big part of our success over the last few years.”
Warne wanted Diagouraga, 29, to come to New York Stadium in the January transfer window, but the former Brentford man has chosen to move to Ipswich Town.
“I spoke to him,” the interim boss said after the St James’ Park reverse. “He texted me today to say he is going to Ipswich.
“I don’t know what else to say. As much as I try to sell myself and the club, if the player chooses a club higher in the league, what can I do?
“He’s not a Rotherham fan, he has no allegiance to us. We tried to do everything we could to bring him here. As it stands, he has chosen Ipswich, so I wish him all the best.”
Warne, who brought in goalkeeper Richard O’Donnell last week, is aiming to make at least two more signings before the window closes on January 31.
“I am hoping to get a couple more in the door next week,” he said. “We are a little bit threadbare at the moment. We need help, we need some fresh faces.
“We are not as close as we would like. Everyone is challenging for the same players.”