"Two clubs have contacted us and he could be moving on loan, it's up to the boy," confirmed Reid.
Mills was not included in the team that drew 2-2 with Newcastle last week and has also been left out of Saturday's trip to White Hart Lane.
The 26-year-old said on his official website that he wanted an explanation for his exclusion, to which Reid has today responded:
"I read his article and I don't want to get involved in a slanging match with players, but I have never questioned Danny's attitude in training, it's been excellent.
"We did have a talk about his quality of performances in games though.
"I pick a squad that I think is going to win the game and he hasn't been in it for the Newcastle game and he's not in it for this one. I think there's a lot of players in that situation."
Reid maintains that he will only pick players on merit, and the former Charlton star's performances in pre-season were not up to his normal high standards.
"He is smashing in training but I haven't seen that in games. I can only pick the team on what I see.
"I am not going to tell him he hasn't got a chance of playing in this team again, I am not that daft. I will look at him in games and I am sure he will improve, but I can't pick him on what I have seen of him in recent matches.
"If he goes on loan he will be playing for someone else, but if he stays here then it is clear to him that the players pick the team on their performances."