Controversial striker Nile Ranger has failed to win a contract at Rotherham.
The 23-year-old, who has a lengthy rap sheet both in the game and in his personal life, had been invited to train with the Millers last month after his exit from Blackpool had been formally agreed.
Warnock had sent mixed messages about a potential deal for Ranger, saying he was only at the Millers to gain fitness before saying he would look at his situation in several weeks.
But the Millers boss has now made a definitive decision on Ranger, though gave the striker hope for the future.
"We're not going to take him on," Warnock said. "It's nothing to do with his reputation. What I've said to him is, we haven't really got time. He's a couple of weeks from Championship-level fitness.
"If I'm at the club - or wherever I am - in the summer, he's quite welcome to come and do a pre-season with me and see what happens from there.
"His attitude has been good with me.
"He shouldn't be where he is at the moment with his ability. But he's done well here.
"One or two clubs lower down than the Championship have asked about him so whether he goes to one of those to the end of the season I don't know."
