Sligo Rovers 0 Dundalk 1
Dundalk withstood a nervy finish to claim a precious three points away to ten-man Sligo Rovers.
David McMillan got the only goal of the game for the visitors against a Sligo side that were at a numerical disadvantage for almost the full game.
Sligo Rovers had been given a pre-game boost with the news that suspensions for Raff Cretaro and Craig Roddan had been served in Saturday's game against Finn Harps, despite that match being abandoned after 20 minutes.
But Roddan lasted just eight minutes before a poor sliding challenge on Daryl Horgan prompted referee Paul McLaughlin to reach for a red card.
Dundalk took just four minutes to capitalise on the situation, with Patrick McEleney and Ronan Finn helping to slice the home side open on the right before presenting McMillan with a routine finish.
Dundalk created plenty more chances but their inability to kill off the home challenge resulted in a breathless finish, as Gavin Peers had a penalty shout waved away when he clashed with Andy Boyle in the area, and Cretaro tested Rogers with a shot from distance.
But they showed their champions pedigree by hanging on for the win and inflicting a first home defeat on the home side in 13 matches.
Sligo: Schlingermann, Adebayo-Rowling, Peers, Leahy, Keohane, Roddan, Kearns, Martin, Sadlier (Russell 67), Cretaro, Campion.
Dundalk: Rogers, Gannon, Gartland, Boyle, Massey, Finn, O'Donnell, Mountney (Meenan 70), Horgan, McEleney (Benson 62), McMillan.
Referee: P McLaughlin.