Stockport missed out on the League Two play-offs despite a thumping victory.
Darlington's Evan Horwood was sent off for a foul on Liam Dickinson in the box which proved the catalyst to the rout.
Anthony Elding scored from the spot, David Poole capitalised on a defensive mix-up to double the lead and Dickinson broke from halfway for the third.
With Bristol Rovers drawing County were in the play-offs, but despite Poole and Elding slotting again, a late Rovers victory stymied Stockport's hopes.
Darlington: Russell, Wiseman, Collins, Phillips (Burgess 46), Horwood, Wainwright, Rowson, Ravenhill, Prendergast (Hardman 82), Giallanza, Joachim (Blundell 46).
Subs Not Used: Stockdale, Wright.
Sent Off: Horwood (34).
Stockport: Lewis, Bowler (Tansey 72), Williams, Owen, Griffin, Poole (Rowe 76), Dinning, Taylor, Elding, Bramble (Pilkington 68), Dickinson.
Subs Not Used: Spencer, Le Fondre.
Booked: Owen, Bowler.
Goals: Elding 35 pen, Poole 49, Dickinson 61, Poole 68, Elding 80.
Ref: G Salisbury (Lancashire).