Swansea City suffered defeat against Leeds United as three first-half goals set the visitors on their way to the three points at the Swansea.com Stadium.
Crysencio Summerville and Joel Piroe had the Yorkshire club 2-0 up inside 10 minutes, and Wilfried Gnonto added to their tally before the break.
Italy international Gnonto would add his second of the evening with 20 minutes to go to complete the scoring.
The Swans had come into the game buoyed by victory over Hull at the weekend and, while they were underdogs against a visiting squad packed with top-flight pedigree, head coach Luke Williams and his players will be disappointed not to have given a better account of themselves and posed more questions of their high-flying opponents.
The Swans had shown one change from that win at Hull City as Bashir Humphreys came in for Kyle Naughton.
Leeds had the better of the opening exchanges but were fortunate in the manner in which they took an eighth-minute lead.
Swansea were unable to clear the ball and when it was worked to Summerville he cut inside to get away a shot that beat Carl Rushworth via a big deflection off Jay Fulton.
Less than two minutes later it was 2-0, Swansea were cut apart down the right and Gnonto was able to play in Piroe – a late replacement for Patrick Bamford in the visitors’ line-up - to fire the ball beyond Rushworth, who got an arm to the shot but could not keep it out.
Swansea needed a quick response, and they had an opening when Fulton won the ball back and it fell to Jamie Paterson. The midfielder looked to feed in the onrushing Ronald, but the final pass had just too much on it.
But the hosts needed Rushworth to make an important save to deny Gnonto, after a Swansea corner routine had gone awry and Leeds attacked in numbers to end with a three on one.
Fulton had a volley blocked from a half-cleared free-kick at the other end, while Ronald should have done better with a volley of his own when Liam Cullen’s header fell for him at the far post.
But Leeds further extended their lead in the 36th minute, a ball in behind found Gnonto’s run and he turned inside Ben Cabango before drilling a low shot into the bottom corner.
Rushworth soon saved from Georginio Rutter as the visitors continued to threaten with the Swans having a mountain to climb as they headed to the changing room at half-time.
The second half started in scrappy fashion, although Swansea built a decent spell of possession in the Leeds half without initially managing to create a chance of note.
Paterson steered the ball narrowly wide after Ronald had cut onto his left foot to send a low effort goalward, before the midfielder fired over the bar after excellent work by Przemyslaw Placheta and Cullen had found him unmarked eight yards out.
Summerville sent a curling effort well wide at the other end as the hour mark passed, and Leeds would have the final word by adding their fourth goal on the counter as Gnonto sent a low right-footed shot into the far corner after being freed by the ever-alert Summerville.
Swansea City: Carl Rushworth, Jay Fulton (Joe Allen 61), Ben Cabango, Matt Grimes (captain), Jamie Paterson, Josh Tymon, Przemyslaw Placheta (Ollie Cooper 78), Liam Cullen (Jerry Yates 61), Nathan Wood, Bashir Humphreys (Kyle Naughton 78), Ronald (Charles Sagoe Jr 78).
Unused Substitutes: Andy Fisher, Charlie Patino, Mykola Kuharevich, Filip Lissah.
Leeds United: Illan Meslier, Junior Firpo, Ethan Ampadu (captain), Glen Kamara, Crysencio Summerville (Jaidon Anthony 73), Joe Rodon, Joel Piroe (Joe Gelhardt 87), Archie Gray (Connor Roberts 77), Georginio Rutter (Mateo Joseph 77), Wilfried Gnonto (Dan James 73), Ilia Gruev.
Unused Substitutes: Kris Klaesson, Charlie Cresswell, Liam Cooper.
Referee: David Webb
Attendance: 17,897
