Derby's relegation worries deepened after Harvey Elliott's strike condemned them to a damaging 2-1 defeat at Blackburn.
Wayne Rooney's side went ahead against the only team in worse form in the last six games when former Rovers loanee Tom Lawrence headed in from close range.
They looked comfortable for spells afterwards but gave away two soft goals that turned the game in Blackburn's favour, through Sam Gallagher's clever header just before the break - his seventh of the season - and Liverpool loanee Elliott marking his 50th senior appearance in style, profiting after Andre Wisdom needlessly surrendered possession.
These are worrying times for Rooney's men who, despite a decent performance, lost their fourth game in five outings and remain fourth from bottom, four points above Rotherham who have three games in hand.
Rovers can breathe a sigh of relief after surely putting any lingering relegation worries to bed following an encouraging second-half display in particular, which yielded their first win at Ewood since the end of January.
Blackburn captain Darragh Lenihan missed out with a groin strain so Jarrad Branthwaite made his first start since February. The Rams, meanwhile, welcomed back Matthew Clarke and Nathan Byrne.
Adam Armstrong's 20th-minute free-kick was superbly repelled by the outstretched David Marshall, and it proved crucial as Derby went ahead two minutes later when Graeme Shinnie's glorious left-wing cross was met by Lawrence, who powered in a close-range header.
Derby dominated most of the half, toying with Blackburn at times, and Patrick Roberts ought to have ended a slick move with a goal but curled narrowly wide.
And they paid the price three minutes before the break when Barry Douglas curled in an inviting corner that Gallagher was afforded space to skilfully flick a header beyond Marshall.
Louie Sibley went close to restoring the lead moments later with a left-foot drive, but Thomas Kaminski produced a brilliant save, tipping it out for a corner.
Armstrong missed a hat-trick of chances within the first 15 minutes of the restart, with Marshall standing firm all three times.
Marshall was beaten in the 66th minute when Wisdom lost the ball and Armstrong fed Elliott before the teenager hammered into the bottom-right corner for his sixth this season.
Kaminski parried a rasping Lawrence free-kick into the path of Byrne, whose effort cannoned off the post five minutes later before an even better save in the dying minutes saw him superbly tip away Colin Kazim-Richards' downward header.
Byrne's stoppage-time corner went agonisingly close to going straight in, but Kaminski intervened before the last play of the game saw Louie Watson go down in the box, leaving the Rams furious as the final whistle blew.
What the managers said...
Blackburn's Tony Mowbray: "I can't remember playing without the control that we normally had like that for a long time, and yet we won the game. We could have scored a lot more, Adam (Armstrong) could have had a hat-trick tonight, and yet they're a good football team. Good structure in the way they play. We'll take the points, move on, four to go.
"After we scored, it gave the team a bit of confidence, because they came with a gameplan. They played a transition game, dropped Lawrence in and they had a front four that looked like they could all break away in the first half. Listen, I'm just happy to take the points. I think they're a good side, they obviously have to win a game or two themselves before the end of the season but there's good signs for them. For us, important to get the 50 points. We've got four games to see how many we can get to, potentially another 12."
Derby's Wayne Rooney: "I've seen the replay and it's the most clear penalty you could ever see. I didn't need to see a replay. Where I was stood, the fourth official was stood right beside me, the referee's got a great view of it, and it's completely unacceptable, the decision to not give a penalty. Listen, I know referees, it's a tough job, I respect that. They get decisions wrong at times, but this one is completely unacceptable.
"If my players don't have a good game, don't do what you ask, I'll deal with it and take action to deal with that. I don't really want to go this route, but Alan Wiley has to take action, because that is unacceptable. I've asked to speak to the referee calmly, I'm not going to go in shouting and rant. All I wanted is an explanation into how he can't see it's a penalty. We didn't deserve to lose the game."