The 36-year-old former Oldham man has not played since November after breaking a bone in his leg. The problem has not healed properly, and Millers manager Ronnie Moore admitted it was a big blow.
"He's struggling. He's going to have another four to six weeks of complete rest so that's a setback," said Moore speaking to Radio Dee dar.
"We could do with Warney because he's lively and we miss him around the dressing room."
Source: BBC Sport