Swansea City Under-18s were defeated on the road in their Professional Development League clash against Sheffield United at Shirecliffe.
The Blades had the advantage inside 20 minutes as Lamine Sidibe volleyed home from a Sam Aston corner-kick.
Aston went on to assist two further goals in the first half, setting up Jayden Prunty and Seth Okyere.
Ramon Rees-Siso had got the Swans back to 2-1 at one stage, but it was not enough for the visitors at the end of a busy and challenging week.
There had been four changes to the starting XI that faced Millwall in the PDL Cup final on Wednesday. Teo Minchev, Aidan Higgins, Carter Heywood and Brogan Popham were those to come into the team
The hosts had the first chance of the afternoon after a period of pressure inside the Swansea box. A header from Ethan Cummings glanced the top of the bar before Sidibe turned an effort straight at Kit Margetson from close range.
And the Blades were rewarded for their good start when a corner from Aston found Sidibe at the back post, where he volleyed home first time.
There was almost an instant response from the visitors as United lost the ball at the back, but the Trialist between the sticks got down to prevent Sammy Henia-Kamau rounding him to slot into the net
Despite a positive spell from the Swans, the Blades got their second goal from another corner from Aston. This time, Prunty was in the right place to head home.
The goals kept coming thick an fast. Swansea's Rees-Siso cut the deficit back down to one goal as his strike found the bottom corner.
But, with seconds remaining of the first half, United had a third with Aston claiming his third assist of the fixture by setting up Okyere to fire into the net at the back post.
After a goal-filled first half, the second half was a much tighter affair and chances were few and far between for either side.
As the game approached the last 15 minutes, in-form Aston fired over and Sidibe saw a powerful effort pushed away from a tight angle as the Blades took the three points on home turf.
Swansea City Under-18s: Kit Margetson (captain), Teo Minchev, Josh Pescatore, Jacob Cook, Iestyn Jones, Brogan Popham, Carter Heywood, Harlan Perry, Sammy Henia-Kamau, Ramon Rees-Siso, Aidan Higgins.
Substitutes: Milo Robinson, Callum Deacon, Bobo Evans, Harvey Gray.