Paul Warne felt his side showed MK Dons too much respect in the first half at Stadium MK on Saturday.
Two early goals from Alex Gilbey and Joe Mason fired Dons into a 2-0 lead, and they could have been high and dry by the break but for some good saves from Daniel Iversen.
Rotherham looked renewed in the second period with the introduction of Freddie Ladapo and Kyle Vassell, and the former netted twice and missed a penalty as Rotherham completed the turnaround.
Speaking afterwards, manager Warne said: "We started the game really poor, which was frustrating. I did not recognise my players in the first 20 minutes. We showed them a little bit too much respect. They are really good footballers.” Warne added.
“The second-half performance was more like us. If we lose football games, I can accept it if we play the way we like to play but the first half was not like us. We made changes and the subs came on and had a real positive effect.
“Our second half performance was excellent. We did say to the lads to move the ball out wide quickly and switch play to get crosses in and we did not do that in the first-half.
“We took the shackles off at half-time and we were causing problems. It was a much better performance from us in the second-half."