The 21 year old returned home after a fall out with Posh boss Grant McCann, but due to the terms of his loan, won't be available for selection by the Millers for the rest of the season.
Speaking to the Star, boss Paul Warne say's the youngster has to toughen up.
“He wants to be a centre-half, He is a great kid. He wants to learn. He is still early in his professional career. But to be a centre-half I think you have to be ugly. It helps if you have no teeth, and I just don’t think he’s got that in him yet. I hope the more training he does with us, the more it will develop him as a player.”
“There was a fall-out, Dom has given me his account. I’d like to believe him. There is always 10 per cent fluff."
“We will train him, we will do extra work and he has an opportunity to win over the staff and go into the summer in a good position.” he added.