Millwall's Under 23s were defeated 4-1 by Coventry City in the Professional Development League on Monday afternoon.
Julien Dacosta, Fabio Tavares (2) and Marco Rus' strikes secured all three points for The Sky Blues, with Alfie Allen's goal on 76 minutes acting as no more than consolation for Kevin Nugent's side.
New signing Seb Drozd played 45 minutes at The Alan Higgs Centre.
Millwall: Wright, Walker, Tiensia, Garande, Okoli, Topalloj, Davis, Allen, Briscoe, Leahy, Boateng. Subs: Drozd, Gillmore, Adom-Malaki, Esse, Cotton.