Linked with a move to the City Ground throughout the summer, Doncaster's valuation of Mills has not been met by Nottingham Forest despite Billy Davies' admiration for the player.
Now Reading look to have slipped in under the radar and agreed a fee for the 23-year-old.
If a deal is done in time for the opening day of the Championship season it will be Forest's strikers looking to find a way past Mills at the Madejski Stadium.