Despite a second-half mini revival, three first half goals saw Swansea City lose 1-3 to rivals Cardiff City in the Professional Development League Two.
A brace from Rhys Healey and an own goal by Scott Tancock saw the visitors go three up before half-time, but the Swans responded through Rory Donnelly in the second-half.
Healey opened the scoring with a tap-in from close range before Tancock doubled the visitors' advantage with an own goal in the 22nd minute.
Healey then added his second and Cardiff's third with a drilled shot past Swans goalkeeper David Cornell into the corner.
Despite going into the midway point three down, the Swans responded in the second-half and were rewarded for their efforts when Donnelly capped off a superb run with a fantastic strike from an acute angle.
SWANSEA CITY U21s: David Cornell, Liam Shephard, Jernade Meade, Oscar Sielva, Keston Davies, Scott Tancock ©, Kenji Gorré (Gwion Edwards, 86), Sam Evans (Henry Jones, 45), Josh Sheehan, Rory Donnelly, James Loveridge.
SUBS: Oliver Davies, Ryan Hedges, Kris Scott.
CARDIFF CITY U21s: Simon Moore, Luke Coulson, Simon Lappin, Theo Wharton, Ben Nugent, Deji Oshilaja ©, Matts Daehli (Brad Williams, 45), Rhys Healey, Andreas Cornelius (Josh Yorwerth, 89), Thomas O'Sullivan, Jaye Bowen (Kane Owen, 85).
SUBS: Ben Wilson, Dane Griffiths.
On a crisp January evening at the Liberty, Cardiff City opened the scoring inside the sixth minute in the second South Wales derby of the development season when Rhys Healey tapped home from close range.
Swans goalkeeper David Cornell managed to parry away Andreas Cornelius' initial header, but Healey was on hand to tap home the rebound from a yard out.
Only minutes later, the Swans almost replied through James Loveridge after Josh Sheehan teed the winger up on the edge of the 18-yard area, but Loveridge skewed his shot wide.
However, Cardiff's advantage was doubled when Scott Tancock put into his own net in the 22nd minute. The Swans skipper attempted a back pass, but despite Cornell's best attempts to rescue the pass, the ball crossed the line.
Then the visitors made it 0-3 when Healey got his second of the game, driving a shot low and hard past Cornell, moments after slicing a previous attempt wide of the target.
Five minutes before the interval, the Swans went close to pulling a goal back when Loveridge found himself in some space inside the box, but the winger's first-time effort was well saved low down by Simon Moore.
HALF-TIME: Swansea City 0-3 Cardiff City
The Swans started the second period on the front foot with another chance to claw a goal back falling to Loveridge. The young winger used his pace to get away from his marker, but Moore did well to turn Loveridge's shot wide.
In the 64th minute, Cornell made a superb stop to deny Cornelius from adding to Cardiff's lead. The striker smashed a shot across goal, but Cornell - at full length - managed to to finger-tip the ball onto the woodwork.
Then, at the other end, Cardiff captain Deji Oshilaja received his marching orders after bringing down Sheehan, just as the Swans number '9' went through on goal. Liam Shephard stepped up to take the free-kick, but he struck straight into the wall.
With just over ten minutes left on the clock, the Swans were finally rewarded for their second-half domination of possession through a goal by Rory Donnelly. The Northern Irish striker did brilliantly well to take on his man down the right-hand side before drilling his shot into the far corner from a very acute angle.
In the 87th minute, Donnelly nearly set the game up for a grand finale when the ball was fizzed into him inside the box, but the striker hit his first-time effort straight down the throat of Moore.