Down lost out on promotion from Division Three as they went down 0-10 to 1-06 to Louth in their final match of the Football League at Pairc Esler.
The Mournemen lie second in the table but the winners of next week's delayed game between Westmeath and Louth will join Laois in being promoted.
Down trailed 0-4 to 0-3 at half-time and were six behind before Darren O'Hagan netted a second-half goal.
They moved to within a point but were unable to secure an equaliser.
Ryan Johnston and Conor Poland knocked over early points in a low-scoring first half but Declan Byrne replied for the visitors.
Caolan Mooney restored Down's two-point lead but eight unanswered points from Louth put them in control.
Five of those points came from Sam Mulroy, with James Califf (2) and Tommy Durnin helping keep the scoreboard ticking over.
O'Hagan netted midway through the second half to leave it 0-9 to 1-3 but Fergal Donohoe pointed to put four between the sides.
Connaire Harrison with a free, Paul Devlin and O'Hagan added to Down's tally, but the final whistle signalled the end of Down's hopes of an immediate return to Division Two following their relegation last season.
In his first season at the helm Paddy Tally had guided Down to five consecutive wins following a defeat by Laois on the opening weekend of the campaign.
In Sunday's other Division Three encounters Westmeath beat Longford 1-14 to 1-0 and Offaly were 1-11 to 1-10 victors at Sligo.