Millwall's Under 23s suffered derby defeat at Calmont Road on Tuesday afternoon following two second-half Crystal Palace goals and a game-changing red card.
A neat finish from Lewis White gave Kevin Nugent's young Lions the advantage inside two minutes, but a straight red card for Harry Donovan early in the second half led to Brandon Pierrick and Levi Lumeka handing The Eagles the three points.
The game had barely picked up pace when Millwall drew first blood, capitalising on space in the area to take the lead. Donovan delivered a terrific ball from the midfield towards White, who took it onto his right foot and slotted past Dion Henry in the Palace goal.
Chances came few and far between for the remainder of the half, with Jiri Skalak - given 75 minutes along with Alex Pearce - testing Henry with a tricky cross-shot, and Kian Flanagan forcing Dave Martin into a smart near-post stop.
The second 45 minutes would be where the pendulum swung in favour of the visitors, as Donovan's strong challenge on Trick Mitchell was controversially deemed worthy of an immediate sending-off by the referee.
Despite a committed defensive display from Nugent's youngsters, Palace found an equaliser just after the hour when good work from Lumeka enabled the attacker to play Pierrick in for a tap-in, for which he duly obliged.
With the majority of the play continuing in The Lions' half, the visitors eventually found the breakthrough seven minutes from time, as Lumeka side-footed home a neat strike to tilt the game Palace's way.
Millwall attempted to salvage a point towards the final whistle, but Mich'el Parker's deflected strike from the edge of the area - saved by Henry - was the closest the hosts came.
Nugent's side now sit fifth in the Professional Development League South, four points outside the top two with a game in hand.
Millwall: Martin; Parker, Nelson, Pearce (Mitchell 75'), Tiensia; Skalak (Harvey 75'), Hanson, Donovan (c), Saunders-Henry; White, Alexander. Subs not used: Sandford, Skeffington, Duncan.