Although Rotherham were well beaten in the end by goals from Andreas Weimann, Christian Benteke and Fabian Delph, they competed well in the first half and could have opened the scoring, but Alex Revell missed two good opportunities.
"To create cup upsets you have to go in front, it's Roy of Rovers to think you can come from 2-0 down," he said.
"We had to go in front and put pressure on Villa so it was very hard went we went behind.
"For 25 minutes we were by far the better side, we had two or three good chances, dominated possession, but we made a mistake and they had the quality to hurt us.
"It's two mistakes for the first two goals, we have to accept that the first one was an incredible finish and the second one, well there aren't many better players than Benteke to head that in at the far post.
"When they got the second it was a long night for us and we were chasing the ball a lot."