The Swans suffered a third defeat in a week as a Harry Wilson brace earned Derby County a 2-1 victory at Pride Park.
After home losses to Norwich City and West Brom, Graham Potter’s side were beaten again as the Wales international struck twice in the first half.
Wilson, on loan from Liverpool, fired in a thunderous effort from 25 yards to open the scoring in the 31st minute.
The midfielder added another 10 minutes later as he intercepted Oli McBurnie’s pass before finding the bottom corner from the edge of the box.
An own goal from Fikayo Tomori pulled one back for the visitors in the 87th minute following a Matt Grimes corner, but it proved too little too late for the Swans.
Defeat left the Swans on 26 points from 20 games.
Potter made two changes to the starting side as Declan John was handed only his second league start for the club.
In midfield, Jay Fulton returned in place of Leroy Fer, who dropped to the bench.
There was no Wilfried Bony in the travelling party as the striker, who had only recently returned from a long-term injury lay-off, was given a rest having made two substitute appearances in the last week.
Derby made a quick start to this encounter, and had the ball in the net after just four minutes – only for Richard Keogh to be ruled offside.
At the other end, Daniel James went close to breaking the deadlock as he outpaced Keogh to reach McBurnie’s ball down the right flank.
The winger, though, saw his effort loop over keeper Scott Carson but bounce along the face of goal.
James then linked up with McBurnie to tee up Fulton, only for the Scot to slide in and see his shot blocked by Carson.
It proved an important save as the Rams took the lead seconds later.
Wilson picked up possession on the right flank and cut inside before firing an unstoppable effort past Erwin Mulder into the corner of the net.
The visitors went in search of an equaliser with John breaking inside from the left and firing a low, right-footed effort wide of the far post.
Derby could and should have doubled their lead shortly after as Scott Malone’s low cross found Craig Bryson, but he scooped over from 18 yards.
But the Rams did get their second before the break as McBurnie saw his pass intercepted by Wilson and he jinked into the box before slotting into the far corner.
It didn’t get any better after the break for the Swans, who were thankful for Mulder two minutes into the second half as he denied Wilson a hat-trick.
Fellow Welshman Tom Lawrence then drilled a fierce free-kick just over the crossbar before McBurnie saw his header from Connor Roberts’ cross kept out by Carson.
Potter threw on Leroy Fer, Jefferson Montero and Barrie McKay as he injected further attacking options.
There was more of a spring in the Swans’ step, with Montero heading into the sidenetting and Fer also going close from a corner.
And when Tomori bundled Grimes’ corner into his own net, the Swans had some hope.
But it proved too late for Potter’s side as they made the trip home to South Wales on a losing note.
Derby County: Scott Carson, Jayden Bogle, Fikayo Tomori, Richard Keogh (capt), Scott Malone, Craig Bryson, Tom Huddlestone, Mason Mount (Max Bird, 90), Harry Wilson (Duane Holmes, 90), Tom Lawrence, David Nugent (Florian Jozefzoon,74).
Subs: Kelle Roos, Martyn Waghorn, Alex Pearce, Calum Macdonald.
Swans: Erwin Mulder, Joe Rodon, Mike van der Hoorn (capt), Cameron Carter-Vickers (Jefferson Montero, 54), Connor Roberts, Jay Fulton (Leroy Fer, 54), Matt Grimes, Declan John (Barrie McKay, 68), Bersant Celina, Daniel James, Oli McBurnie.
Subs: Kristoffer Nordfeldt, Kyle Naughton, Martin Olsson, Joel Asoro.