Jack Marriott scored his second goal in as many games as Derby prevented Sheffield United from returning to the top of the Sky Bet Championship with a 2-1 win at Pride Park.
Craig Bryson netted the fastest goal in the EFL so far this season after 19 seconds to stun the Blades early on, but Chris Basham levelled proceedings four minutes before the break as he tapped home John Fleck's cross.
The Blades had dominated the closing stages of the first period, but lacked a certain vigour following the restart and Marriott cleverly flicked home Craig Forsyth's left-wing cross to secure the home win.
Derby: Carson (6), Bogle (6), Tomori (6), Keogh (6), Forsyth (6), Bryson (7), Huddlestone (6), Wilson (6), Mount (8), Marriott (8), Waghorn (6)
Subs: Lawrence (6), Jozefzoon (n/a), Davies (n/a)
Sheffield United: Henderson (6), Stevens (6), O’Connell (6), Basham (7), Egan (6), Freeman (5), Fleck (6), Norwood (6), McGoldrick (6), Duffy (6), Sharp (5)
Subs: Clarke (n/a), Coutts (n/a), Washington (n/a)
Man of the match: Mason Mount
Frank Lampard's Rams sit fifth as a result of the victory, with United's inferior goal difference placing them second behind Middlesbrough.
The visitors were stunned into silence immediately when they afforded the hosts space to carve a slick opener from kick-off, Marriott cushioning Harry Wilson's cross and Bryson striking the quickfire opener past Dean Henderson.
With the break approaching, Chris Basham - one of United's rampaging 'false number five' centre-backs - tapped Fleck's cross into an unguarded net after Scott Carson was drawn in by the Scottish midfielder's meandering run.
Despite having been behind, United hadn't capitulated, yet Derby were keen to not simply rest upon their laurels and continued to display their deadly ability on the counter attack.
In the 54th minute, Tom Lawrence latched onto Bogle's defence-splitting pass and drew Henderson into a magnificent save, before Lawrence spotted the run of fellow substitute Florian Jozefzoon with the Dutchman denied by the last-ditch toe poke from Enda Stevens.
Sheffield United boss Chris Wilder made no alterations to his side that topped the Championship during the international break, while for the Rams, Bradley Johnson, Florian Jozefzoon and Tom Lawrence made way for Martyn Waghorn, Tom Huddlestone and Harry Wilson.
Lampard's side continued to knock on the door and did finally score what proved to be the winner after 77 minutes when Forsyth delivered a tempting cross and Marriott leaped to flick home an excellent improvised effort.
Frank Lampard: "It [Marriott's winner] was top-class, as good as they come. For a goalscorer to get across your man at pace and to guide it into the far corner as he did is a really difficult skill, and I didn't realise how good it was until I saw a replay.
"I'm demanding of centre forwards because I want them to work for the team, they can't just think about goals. Jack was probably a bit short on fitness when he got here so that took a few weeks, but he loves practising and he's improving because the more you practice, the more you improve.
Chris Wilder: "It's a great result for Frank and Derby and a poor one for us. It was a tight game between two really good sides and they found their moment..
"Derby were better than us second half. We lost control of the game a little bit but I thought we were really good in the first. I've no complaints about the second half and the result overall because if you defend like that and don't put teams to bed the result can go either way."
The Rams face a tricky trip to the Hawthorns to face West Brom on Wednesday evening, while Sheffield United welcome Stoke to Bramall Lane the previous night. Both matches are available to view on Sky Sport Football red button or on the Sky Sports mobile app.