Swansea City could not capitalise on sustained second-half pressure as Brad Potts struck the only goal of the game to give Preston North End victory at Deepdale.
The North End defender fired in what proved to be the winner on the half-hour, with the finish coming via a rebound after Emil Riis had been denied by Steven Benda.
Swansea grew into the game, and were the dominant team throughout the second period, with Jay Fulton and Ryan Manning going closest only to be denied by former Swan Freddie Woodman, while Joel Piroe also planted a header wide as the stubborn hosts kept their 11th clean sheet of the season.
The Swans had shown four changes from the weekend draw at Bristol City as Manning, Kyle Naughton, Olivier Ntcham and Piroe were handed starts.
Matty Sorinola, Nathan Wood, Ollie Cooper and Michael Obafemi dropped to the bench, while the hosts made two changes as Andrew Hughes and Ched Evans came in for Alvaro Fernandez and Ben Woodburn respectively.
It was a cagey opening, with a glancing Riis header flying well wide from the only half-chance of the early exchanges.
But the Swans were handing North End opportunities to counter, and Potts wasted one of those when he squared a ball to no-one in particular after surging down the right.
The visitors had not really got out of the blocks, and they had another let off in the 16th minute when Riis steered wide when he should have scored from a Potts cross.
Swansea’s first chance arrived in the 22nd minute and it was a good one. Fulton fizzed a ball in towards Piroe, who had drifted off his marker, but the Dutchman steered his header wide of the right-hand post.
But it remained the hosts who looked the more likely to find an opener and it came on the half-hour.
Harry Darling failed to deal with Alan Browne’s cross towards Riis, and while Benda saved the forward’s initial close-range shot, he had no chance with Potts’ follow-up.
The Swans looked to respond and it took two good blocks to deny Fulton after slick passing had worked him some room just inside the area.
Manning then did well to meet a deep cross on the far byline and loft it back into a threatening area, but there were no orange shirts there to capitalise.
Piroe and Manning then just failed to connect with another Fulton cross as Swansea enjoyed their best spell of the game so far.
They still trailed at the interval but were again on the front foot early in the second period as Piroe had a shot blocked.
The visitors were having plenty of ball and territory, with the hosts spending long spells pinned in their own third.
Martin went to his bench 10 minutes into the second period as Jamie Paterson and Armstrong Oko-Flex replaced Ntcham and Naughton.
Manning immediately freed Oko-Flex in behind with a good clearance preventing his cross picking out Piroe.
Freddie Woodman then made an outstanding save to deny Fulton after a corner had been cushioned into the Scotsman’s path and he had made firm contact with his strike from 15 yards.
It was all Swansea and most of the joy was coming down the left flank as Manning and Oko-Flex probed away at the Preston rearguard.
Harry Darling's header was held by Woodman as Swansea continued to press, with substitute Ollie Cooper volleying over from Oko-Flex's excellent cross.
Still Swansea surged forward, but it was not to be as time ran out, with Manning being denied by Woodman in stoppage time.
Swansea City: Steven Benda; Joel Latiebaudiere, Harry Darling, Ben Cabango; Kyle Naughton (Armstrong Oko-Flex 55), Jay Fulton (Ollie Cooper 75), Matt Grimes (captain), Ryan Manning; Luke Cundle (Michael Obafemi 70), Olivier Ntcham (Jamie Paterson 55); Joel Piroe.
Unused Substitutes: Andy Fisher, Nathan Wood, Matty Sorinola.
Preston North End: Freddie Woodman, Ben Whiteman (Ryan Ledson 23), Liam Lindsay, Alan Browne (captain), Ched Evans (Sean Maguire 78), Robbie Brady, Ali McCann, Jordan Storey, Andrew Hughes, Emil Riis (Ben Woodburn 86), Brad Potts.
Unused Substitutes: Dai Cornell, Alvaro Fernandez, Greg Cunningham, Daniel Johnson..
Referee: John Busby