RIVAL boss Gary Rowett admitted his side were lucky to leave AESSEAL New York Stadium with all three points as Rotherham United suffered their first Championship defeat of the season.
Millwall won 1-0 on Saturday after being gifted a goal by a rare Michael Ihiekwe error but the Millers should have secured at least a draw.
"I have to say, we probably didn’t do enough in the attacking sense to win the game," Lions manager Rowett conceded.
Jed Wallace grabbed a 50th-minute winner for Millwall who were relieved to see Freddie Ladapo, Kieran Sadlier, Michael Smith, Angus MacDonald and Joe Mattock spurn chances.
"It was a very difficult game," Rowett said. "Rotherham are very good at what they do. They want to drag you into a really physical game which they are really good at. They put a lot of balls into your box.
"The game-plan was to show a lot more composure on the ball and try to get into some good areas, release that pressure and force some pressure of our own. We didn’t do that anywhere near well enough in the first half.
"In the second half we probably did it better. For 25 minutes, we moved them around a little bit more.”
"Were we resilient? Yes. Did we defend well? Yes. That’s what we are good at. But what we have to show is a little more composure.
"We get a little bit of fortune with the goal but Jed antIcipates it well and takes it well. Then we defended for the last 15 minutes and headed balls out of our box . It would have been very easy to crumble under the pressure."
New loan signing from Leicester City George Hirst came on in the 66th-minute for his Rotherham debut and the young striker was denied his first goal for the club only four minutes later by a superb block.
"You can see why I brought George to the club," said Millers boss Paul Warne. "He needs to get used to how we play. He has trained with us for only two days but I think he is a brilliant acquisition.
"Every time the ball goes into him you think something is going to happen. His movement is really quick. He is mature as a player and person and I think he will be great for us."