Derby County's Under-21s fell to a 3-2 defeat to Brighton & Hove Albion Under-21s in Premier League 2 on Friday evening.
A second-half brace from substitute Alex Gibson-Hammond looked to have secured the Rams a point at Alfreton Town's Impact Arena, but a stoppage time strike from Louis Flower ensured it was the visitors that would return home with the three points.
Brighton had an excellent chance to take the lead inside the opening five minutes when Mark O'Mahony scuffed an effort into the arms of goalkeeper Harry Evans following a cut-back from the left.
That same man was causing problems and he nicked in front of Evans to direct an effort towards goal but there wasn't enough on it and defender Daniel Cox was able to clear.
The visitors made their early pressure count as they took a deserved lead when Jamie Mullins finished off a neat move from the centre of the box.
Jake Buxton's men nearly equalised instantly but Riley Moloney's dipping effort from just outside the box went narrowly over the crossbar.
Brighton doubled their lead after 30 minutes through Mark O'Mahony. Luca Barrington's first-time cross was put on a plate for the striker who slid in and steered past Evans, who had no chance.
The Seagulls had the ball in the net for a third time before the break through O'Mahony once again but he was denied his second and Brighton's third by a hastily raised offside flag.
Derby had an excellent opportunity to cut the deficit in half within the first minute of the second period. Winger Carlos Richards delivered a superb set-piece onto the foot of experienced player-coach Bradley Johnson but the midfielder couldn't direct his effort on goal.
Cox headed narrowly wide from a corner and Tony Weston fired inches past the post as the Rams continued to press in the early stages of the second-half.
Derby got what they deserved for a promising second-half performance when substitute Gibson-Hammond halved the deficit with a rocket of a strike just moments after coming off the bench. He picked the ball up on the left and fired a superb strike into the top right corner from just inside the penalty area.
Within 10 minutes the game was all square. Gibson-Hammond stooped low to head home Dajaune Brown’s cross and level the scoreline with five minutes of normal time still remaining.
The summer signing from Nottingham Forest was inches away from his hat-trick soon afterwards too. He got in behind his man and headed a strong effort towards goal but it cannoned back off of the crossbar and away to safety.
The Rams had worked incredibly hard to get back into the game and were cruelly undone by a set-piece in injury time. A corner was whipped in and Brighton substitute Flower was first to a second-ball to poke home from six yards out and snatch all three points for the visitors.
Derby County Under-21s: Evans (GK), Moore, Jeffcott, Johnson, Radcliffe (C), Cox, Richards (74' Wheeldon), Fapetu, Brown, Weston (90' Lindsay), Moloney (74' Gibson-Hammond).
Substitutes Not Used: Ridd (GK), Bates.
Brighton & Hove Albion Under-21s: Cahill (GK), McConville (77' Nilsson), Slater, Jackson, Kavanagh, Hinchy (C), Baker-Boaitey (81' Ifill), Chouchane, O'Mahony (77' Flower), Mullins (70' Peart), Barrington.
Substitutes Not Used: Ferdinand.