It is too late to save their season, but Shamrock Rovers struck seven goals in Tallaght to register the biggest win on their new ground.
Yet for Dundalk, this was as bad as it gets. Spiritless and, at times, absolutely appalling, they shipped seven goals to register the third worst defeat in their history and the heaviest on home soil since 1944.
Bottom of the league, they have a chance of redemption in the FAI Cup, where somehow they have reached the semi-finals. As for the league, a play-off gives them some hope of an escape. Whether they want it remains a moot point.
Quite simply, they were terrible.
It all started to go wrong on 27 minutes when Ronan Finn, taking advantage of a sloppy clearance from a corner, and an even sloppier attempt to close him down, scored the opener with a 25-yard shot which nestled inside Peter Cherrie's net.
Three minutes later 1-0 became 2-0. Ken Oman, a replacement for the injured Colin Hawkins, ventured forward for a free-kick and got on the end of Killian Brennan's delivery to deftly flick the ball beyond Cherrie.
By the stroke of half-time, there was a third. Finn, involved again, cleverly dissected the Dundalk defence with a threaded pass for Gary McCabe who squared the ball to Ciaran Kilduff -- his finish from six yards was straightforward.
The second half proved even more one-sided as McCabe got two from the penalty spot and Gary Twigg bagged a brace.
Shamrock Rovers -- Jansson; Gannon, Hawkins (Oman 22), Sives (Greene 68), Powell; McCabe (Dennehy 82), Finn, Rice, Brennan; Kilduff, Twigg.
Dundalk -- Cherrie; Mountney, Whelan, Burns, Osbourne; Walsh, O'Brien (Conlon 65), Shields, Maher, Murphy (McDonnell 65); Rafter (McKenna 79).
Ref -- D Hancock (Dublin)