Why Julien Lamy has yet to make his debut for Rotherham United
Warne wants the 19-year-old to build himself up in body and mind after suffering a serious injury in the summer and only then will he declare him ready to play.
In the meantime, the boss is happy to include Lamy in his squad so the youngster can familiarise himself with the matchday experience.
"I'm not going to divulge every detail of every player I have," said Warne. "That's not fair. Julien got a severe leg problem and hasn't been fully fit yet.
"I'll put on only the players who I think are physically and mentally ready to play and only if the game situation is suited to them.
"I don't think that in any of the games where Julien has been among the subs it has been the right time to bring him on.
"He's on the bench because I want him to get used to the first-team matchday environment. I'll involve as many players as I can in that because I think there's always something to learn from just being at a game."
Some supporters are frustrated by Lamy's absence, believing the winger, who signed a season-long deal after a successful trial, could offer an exciting flank threat if he was let off the leash.
"I can understand why fans think like that," Warne said. "Oddly enough, if I thought Julien could have that kind of impact now I would put him on.
"I really like wingers who can go past people and cross the ball. When I think that Julien is ready to do that at first-team level, he will get the opportunity to play.
"Unfortunately for the fans, I have the better view. I see him in every single day. I work with him. I know how he is feeling and where he is at. A few players haven't got on. Julien isn't the only one.
"I've got some really good players at this club. It would be disrespectful to them if I think that he is the answer to all the questions from the fans."
Lamy was able to sharpen his fitness in a reserve clash this afternoon at Doncaster Rovers where he scored in a 4-2 defeat.
"Playing for the ressies will push him on," said Warne. "We need to build him up physically and mentally."
The manager is prepared to give his wide man his first taste of senior action late on in a match but only if a win is already in the bag.
The home triumph over Bolton Wanderers on September 14 would have been an ideal opportunity to blood him had it come later in the schedule.
"For the Bolton game, even though we won 6-1, he was nowhere near ready because he wasn't fit enough so he couldn't have come on," Warne said.
"Against Shrewsbury Town a week afterwards (0-0 draw), had we been three goals up and there had been an opportunity to put him on at the end then I would have done.
Lamy was called into the squad because a raft of injuries meant that Rotherham were struggling to name a full quota of 18 players.
Warne added: "He's on the bench because I'm not the kind of manager to leave three places spare and give it: 'Look at me and how many injured players I have got.'
"I try to fill the bench with players who will gain something from being there. If nothing else, it means they're around the squad and know what is expected of them when they do play.
"We have meetings before the game, at half-time and after the game. I want my players to be involved in all of that as much as possible. Sometimes I might have someone on the bench who isn't even fit to play. That's my prerogative.
"If there's chance to use him, then I will. But I want to make sure, for his sake and the club's, that I choose a moment when I believe he is ready."