Millwall U23s were beaten by Watford for the second time this season, falling to a 3-0 Professional Development League defeat at Dartford on Monday afternoon.
An early goal from Dion Pereira set the tone for the visitors to claim all three points in wet conditions.
The midfielder collected the ball on the flank in the 14th minute, played a neat one-two with Harvey Bradbury and drilled low into the back of the net.
It was a confident start from the visitors and Millwall needed time to assert themselves against a team happy to make the contest a particularly physical one.
Kristian Brymora had a glimpse of goal in the shadows of half-time but couldn't draw the hosts level in the rain.
The Hornets' second came in the 66th minute as Harvey Bradbury followed up his earlier assist with a goal after meeting a floated corner at the far post.
Dennon Lewis ended any hopes of a late comeback when he raced clear on goal in the 90th minute and slotted beyond the reach of Ryan Sandford for Watford's third of the afternoon.
Millwall U23s: Sandford, McNamara, Tiensia, Donovan, Debrah, Mbulu, Ajibaye, Hanson, Brymora, Leighton, Olaofe.
Subs: Duncan, Jackson, Sinclair, Skeffington, West