Neil Harris bemoaned a "change of momentum" following Aiden O'Brien's red card in Saturday's 1-0 Sky Bet Championship defeat to Wolves at Molineux, but expressed his delight at how his players dealt with the situation.
Diego Jota opened the scoring in the 10th minute, but with The Lions gaining a foothold in the game early in the second-half, O'Brien was given his marching orders for a second bookable offence.
Despite that, Millwall did have chances to draw the game through substitute Fred Onyedinma and Shaun Williams.
"Football is a strange game sometimes," said Harris. "We were up against it for long spells - especially with 10 men - but we could've stole a point at the end.
"I think we showed too much respect to Wolves in the first-half. We lacked a bit of belief in imposing our style of play, which we addressed at half-time. For the first 20 minutes of the second-half, we looked much better, a lot more Millwall-like.
"Unfortunately, the red card then comes and that changes the momentum of the game again."
Harris said he had "no complaints" with referee Robert Madley's decision.
"I've not seen the red card decision back, but at the time, I had no complaints. The first one is a strong challenge and Aiden knows better than to pull someone back when on a yellow card. That made it an uphill struggle for us.
"But, I'm absolutely delighted with the determination, the passion, the spirit and the character that we showed. We showed great shape with 10 and 11 men."
Tom Elliott was a notable absentee from Saturday's matchday squad, with the manager adding that the striker injured himself in training.
"Tom went down in training with literally the last kick on Friday. Of course, he would've travelled and been a part of the squad, but he will now struggle for Tuesday night's trip to QPR."