This latest disappointment for Micky Mellon's men leaves them four points shy of Aldershot in the final play-off spot, with just five games left to play.
Nick Haughton scored one and created another as AFC Fylde triumphed.
Haughton looked dangerous from the very start as he hit a shot against the crossbar in the sixth minute.
He then put the visitors ahead moments later when he turned in Connor Barrett's cross.
It was 2-0 after 17 minutes when Adam King got his first Fylde goal, turning in a loose ball after a corner.
Haughton then volleyed narrowly wide moments later after creating space for himself.
Ethan Mitchell headed in a third from Haughton's cross in the 32nd minute, before Latics got one back through Dan Gardner just before the break.
But any hopes of a second-half comeback were dashed by a 60th-minute red card for half-time sub Mike Fondop.
Latics boss Mellon said: "We didn't defend well enough, we gave away too many cheap goals and we gave ourselves a mountain to climb.
"And then when you create that environment by the way you give goals away and you find yourself in a really difficult place, it's always going to be tough."
Latics return to action on Easter Monday when they travel to local rivals Altrincham.
