Ben Wiles and Freddie Ladapo came off the bench to score the goals which saw the Millers beat Accrington Stanley on Saturday, maintaining their slender goal difference advantage over the Sky Blues, who have a game in hand.
Manager Warne says it shows the attitude and appetite of those on the fringes of his side, and they put his regulars to the test in a training-ground match last week.
“It's keeping the people on the periphery ready and it pushes the XI,” he said. “We had a game here and the lads not in the first team were better than the first team. That happens quite a lot at every training ground.
“When you have them games, you need the opposition to be good to make it realistic and then you can ask the first team what problems they caused them playing like Accrington. It's a good way to keep them lads match-ready and push the lads in the team.”
As is often the case when a team is in form – Rotherham have won four of their last five matches – the treatment room is a quiet place.
“We've got no injuries, no issues after Saturday,” said Warne. “We were happy to get a win and move onto the next one.
“The squad is ridiculously healthy. Before the game I was talking to Curtis (Tilt) and Trev (Clarke) on the side of the pitch, who weren't even in the 18-man squad. Billy (Jones) is fit and needs a game so we go into the last quarter of the season in good health.”
That strength in depth reflects in the performances of the Millers' substitutes with Josh Koroma, on loan from Huddersfield Town, impressed as much as the goalscorers at Accrington.
“When you want to make a change it's good,” commented Warne. “I could replace any for any and it doesn't make us any weaker. When you make a sub you're just becoming different and fresher.
“On Saturday I put on Josh, Freddie, and Wilesy, who are all outstanding players who all deserved a start but they came on and had a positive effect to help the team and the club to get a victory.
“I didn't feel Smudge imposed himself as much on Accrington's centre-halves, or maybe they preferred the physicality of Smudge (Michael Smith), other defenders don't. The movement of Josh and Freddie was a different problem.
“It's about trying to pick a team we think can win and being able to make changes we think can have a positive effect.
“Josh is a bit of a maverick. When he came on at Lincoln the first thing he did was nutmeg someone and I'm thinking, 'I'm not sure this is going to last well!'
“I think he's getting it a bit more and in finishing and in games he's been excellent and chewing the bit to play. I haven't brought him in to make the numbers up. He's just something different.
“With Vass (Kyle Vassell), Smudge, Josh and Freddie you ask different questions because they're different sorts of players, who all have different strengths and weaknesses. It does add another string to our bow.
“We never say die, we go to the final whistle and if that's the case, whoever comes on late in the game will be in and around the box and the ball, so there are always chances created late on. It's not very often, no disrespect, that I waste a sub changing a centre-half, they're always attacking substitutions so it's no surprise the subs affect it in a positive way.”
And despite leaving good players out of his team, Warne says he has had hardly any complaints.
“I can tell by people's body language if they're in a sulk because they're on the bench and if you are, you can sit there all week and next week you won't sit there at all,” he said.
“I've only had one player knocking on the door because it's a waste of a knock. If you knock on the door when the team is winning, you're just using skin up and damaging my door unnecessarily, so no one's stupid enough to knock on my door and say, 'I should play,' when someone in their shirt is playing so well.”