The 35-year-old centre-half, who has missed the Millers' last 12 matches due to a knee injury, will be back in action for the reserves on Tuesday against Notts County.
"He's back in training and we have a game against a strong Notts County side on Tuesday, so Nayls will play in that," manager Steve Evans told the club's official website.
"It'll be a strong side and will be interesting to see. I need to see performances from these games that tell me which players want to be in the first team."
Rhys Taylor, Danny Harrison, Mark Bradley, Sam Hoskins, Scott Griffiths and Kieron Cadogan are all expected to feature.