Millwall boss Gary Rowett admitted his team were punished for some woeful defending in their defeat at QPR.
The Lions were beaten 3-2 at the Kiyan Prince Foundation Stadium, where they were two up at half-time after goals from Jed Wallace and Mason Bennett.
All three second-half Rangers goals resulted from defensive lapses by the visitors.
Charlie Austin got in front of Alex Pearce to head home Geoff Cameron's cross before Ryan Woods gave the ball away to allow Stefan Johansen to equalise.
And worse followed for Millwall when Jordy De Wijs headed in Ilias Chair's corner four minutes from time.
Rowett said: "In the first half we were excellent. We got to grips with QPR, moved the ball well, had very good chances and took two of them.
"We spoke clearly about maintaining that intensity in the second half. For us to then concede so early in that second half – I thought it was a really poor goal.
"Charlie Austin gets in front of us and for them to score with one ball and one header from quite far out was really disappointing.
"The second goal was equally as poor and for the third we left the man free at a set-piece."
Two misses by Shaun Hutchinson when Millwall were ahead also proved costly for the south London side.
"You have a glorious chance to take the game away from QPR but you don't take it," Rowett said.
"They score quite quickly after that and as soon as they score it gives them a real lift.
"It was a combination of not being able to maintain that energy level and making three really bad mistakes.
"We made mistakes, they punished us and we probably got what we deserved."
QPR manager Mark Warburton praised his team for battling back after an appalling first-half showing.
"I don't rate that first half in any shape or form," he said.
"We were lucky to be only 2-0 down. We played like a team that hadn't even met each other before.
"We gave the ball away cheaply, vacated areas positionally and were naive. It was very unlike us as a team.
"We fully deserved to be two down and it could easily have been more. We looked so far off our normal level.
"To then show that desire and character, and to create so many chances against a Millwall defence that gives away very few chances against most teams in the division, the players deserve so much credit.
"In the second half we were on the front foot, moving the ball much quicker, and the players smelt the victory as opposed to just settling for the point.
"To come back in that fashion – they showed a lot of desire and commitment – they can take huge belief from that performance."
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