Steve McClaren is still looking for his first league win in charge of Nottingham Forest after they were beaten by Millwall at the New Den.
Striker Darius Henderson scored his second goal in as many Championship games to put the Lions ahead when he headed in James Henry's corner.
Forest improved after the break and controlled long periods of possession.
But they were killed off 13 minutes from time when Liam Trotter latched onto Dany N'Guessan's low cross.
Forest needed penalties to beat League One side Notts County in the Carling Cup in midweek, and looked sluggish from the outset.
Henderson capped a bright start for the hosts with the opening goal, while American striker Robbie Findlay hit the post for Forest in the second half as they searched for an equaliser.
But Trotter sealed victory for Millwall when he latched onto substitute N'Guessan's centre from the left to sweep home.