Derby are blessed with quality players all over the pitch but they didn’t even need to get out of second gear as life was made all too easy for them by a Town team who turned in one of their worst performances during Jon Brady’s reign, particularly in the first half.
Max Bird opened the scoring on 14 minutes after being left untracked in the penalty box, Conor Washington then charged through unchallenged for a second before Bird doubled his tally and made it 3-0 for the utterly dominant hosts with barely half-an-hour played.
It resembled more of a training session rather than a competitive League One fixture and worse was to come in the second half with Nathaniel Mendez-Laing scoring a fourth, and Derby really should have notched up six or seven as further chances went begging.
Cobblers are now above the dreaded dotted line by goals scored alone but as poor as they were, and as heavy as the margin of defeat was, they can't let one bad night define their season and now must dust themselves down and move on quickly.
There was just one alteration from the weekend as Ali Koiki came in on the left wing for his first league start, with Jordan Willis the man to drop out.
Derby had all of the early possession and were close to a seventh-minute breakthrough when Washington’s first-time flick from a Tom Barkhuizen cross dropped narrowly wide of the far post.
Cobblers were sloppy on the ball and left too many gaps when Derby attacked and that was always likely to be punished given the home side’s quality. The opener duly arrived on 14 minutes when County sliced through Town with ease and Bird tapped in Washington’s low cutback.
Bird could have added a second minutes later, this time off target after Cobblers were again carved open, but the visitors weren’t learning their lessons and found themselves further behind midway through the first half as Washington drove through the heart of defence and slotted home.
Cobblers were chasing shadows, neither putting pressure on the ball nor tracking runners, and two became three on 32 minutes when another long period of Derby possession ended with Bird ghosting in unmarked and scoring his second of the night.
The hosts went easy on their beleaguered visitors and it remained 3-0 until half-time, but the damage had been done and Brady responded by making a triple change at the break.
Will Hondermarck, Ryan Haynes and Jordan Willis all came on, replacing Manny Monthé, Ali Koiki and Mitch Pinnock.
But that didn’t stop the bleeding and a fourth goal came just four minutes into the second half as Cobblers were ripped apart on the break and Mendez-Laing swept emphatically beyond Lee Burge at the back post.
The onslaught kept coming. Burge was at full stretch to deny Washington a fifth, Barkuizen blazed over and substitute James Collins headed wide after inexplicably being left all alone inside the penalty box.
Derby did ease off in the closing stages and Cobblers were able to survive with no further damage, but it had already been a night to forget.
Derby: Wildsmith, Forsyth, Nelson, Nyambe (Ward 61), Hourihane © (Wilson 68), Bradley, Barkhuizen, Bird (Brown 76), Mendez-Laing (Fornah 68), Smith, Washington (Collins 61). Subs not used: Vickers, Sibley
Cobblers: Burge, Monthé (Willis 45), Sherring, Brough, Koiki (Haynes 45), Odimayo (McGowan 72), McWilliams (Abimbola 57), Leonard, Pinnock (Hondermarck 45), Hoskins ©, Simpson. Subs not used: Thompson, Lintott
Referee: Simon Mather