Millwall's Under 23s were defeated 1-0 by Ipswich Town in the Professional Development League on Monday afternoon.
Idris El Mizouni struck the winner three minutes into stoppage-time to break Lions hearts and condemn Kevin Nugent's side to defeat on their own patch.
Millwall were presented with a huge opportunity to take the lead after just three minutes, but after Nana Boateng crossed for Junior Tiensia, the left-back got his effort wrong and failed to threaten the Ipswich goal.
Tiensia then struck just wide of the near post almost midway through the first-half, before Dan Moss' cross was headed over by George Alexander on the half-hour mark. Reuben Duncan's free-kick was then gathered by the Ipswich goalkeeper at the second attempt as Millwall were the more dominant force in front of goal.
Duncan sent another free-kick just wide of the far post as the half-time whistle blew, with Boateng having the first effort of the second-half, shooting into the side-netting after creating some space for himself for a shot.
Alex Mitchell then had to stand firm to block a couple of Tractor Boys shots, but after Tyler Burey struck over as the closing stages began and a goal looked certain, El Mizouni's effort from range found the net to win the game for Ipswich Town.
Next up for Millwall's Under 23s is a home game with Queens Park Rangers on Tuesday 26th January.
Millwall: Sandford, Moss, Tiensia, Muller, A. Mitchell, Topalloj, Burey, Duncan, Skeffington, Alexander (O'Brien 85'), Boateng (Davis 80'). Subs not used: Gillmore, Abdulmalik, Allen.