Kevin Nugent couldn't hide his disappointment after seeing his side slip to a 3-2 Professional Development League defeat over Charlton Athletic at The Den on Monday afternoon.
Goals from Seb Drozd and Zak Lovelace put Millwall's Under 23s into a 2-0 lead, but a late fightback from the visitors saw three goals scored in the final 15 minutes to turn the game on its head.
"I hate saying this phrase, but it was a game of two halves," Nugent told millwallfc.co.uk. "In the first-half, I thought we did very well and could've been more than 2-0.
"They were passing through us a bit too easily, but we addressed that at half-time. However, unfortunately in the second-half, we reverted to being 11 individuals. The players were all over the pitch. No one showed real personality to take hold of the game. It wasn't overly nice in [the dressing room], they're going to have to learn from that quickly."
Despite the loss, The Lions' Academy is thriving, with the likes of Lovelace, Nana Boateng and Besart Topalloj all in and around the first-team squad, plus Dan Moss and Alex Mitchell - among others - excelling on loan.
"Right from the young ages, all the way up to the Under 23s, everyone is working hard. It's great these lads are now getting the opportunity. That's the positive side of it, but they need to remember that when they're playing with us, they stay at that level and keep pushing the first-team players."