Millwall's Under 23s lost 1-0 to Leeds United in the Professional Development League at Calmont Road on Monday afternoon.
Alfie McCalmont's goal just before the end of the first-half wrapped up all three points for the visitors.
David Martin and Byron Webster started in the young Lions' XI, whilst new signing Jem Karacan took his place in the centre of midfield.
A quiet first-half saw little in the way of clear-cut chances until McCalmont opened the scoring with a low drive in the 42nd minute.
Mason Saunders-Henry, Rob Harvey and Joe Wicks attemped to get Kevin Nugent's side back in the game in the second-half, but to no avail.
Millwall: Martin, McNamara, Wicks, Karacan, Webster, Stojsavjlevic, Harvey, Hanson, Campbell-Parker, Olaofe, Saunders-Henry. Subs: Debrah, Sandford, White, Davison, Parker.
Leeds United: Huffer, Gotts, Davies, Shaughnessy, Struijk, Diaz, Roberts, Rey, Edmondson, McCalmont, Clarke. Subs: Miazek, Stevens, Dalby, Sarkic, Nicell.
Referee: Mr D. Lamport