|Venue: The Den
|Vydra 26, Guedioura 56|
MILLWALL were undone by two moments of quality as their hopes of staying up were dented by Watford.
The Lions were holding their own against the promotion-chasers until Matej Vydra's clinical first-half volley edged the Hornets in front.
And Adlene Guedioura struck early in the second period to put the visitors in a commanding position and knock the wind out of Millwall's sails.
The Lions, who remain seven points adrift of safety, went closest to reducing the deficit when Aiden O'Brien was denied by Heurelho Gomes in a one-on-one situation.
Interim boss Neil Harris was forced to make one change to his starting line up, with Jos Hooiveld, scorer of the winning goal against Charlton, ruled out through injury.
Left-footer Mark Beevers was selected to partner the right-sided Sid Nelson at centre half, while Lee Martin also returned to the squad as a substitute following a broken metatarsal.
Watford, full of confidence after beating fellow promotion-hopefuls Middlesbrough on Monday, almost took the lead within the first 90 seconds.
Troy Deeney latched onto Daniel Tozser's diagonal pass after drifting off the shoulder of Beevers but David Forde came off his line quickly to smother the striker's shot.
At the other end, Lee Gregory almost latched onto Ed Upson's clever pass down the left-hand channel but he was narrowly beaten to the ball by Gomes.
Shaun Williams' corner was then dangerously hooked back across goal by Martyn Woolford before Gregory shot wide on the turn from inside the box moments later.
Deeney wasted another good chance in the tenth minute when he looped a header over Forde's bar from Guedioura's inviting cross.
Millwall had fervent calls for a penalty waved away in the 16th minute when Upson was bundled over in the box.
And the Hornets then took the lead when Ikechi Anya got the better of Shaun Cummings and crossed for Vydra, whose sweetly-struck first-time volley nestled in the bottom corner.
Ben Watson could have added a second goal for the visitors soon after but he sliced miles wide from a good position.
After riding out another ten minutes of pressure, the Lions began to edge their way back into the contest as half time approached.
Martyn Woolford did well to intercept at the feet of Gomes but he was unable to find O'Brien with a cut-back, and the winger then saw a half-volley well-held by the former Tottenham stopper.
Jimmy Abdou's low drive was tipped behind by Gomes on the stroke of half time as Harris's side were clapped off by the fans at the break.
Williams sent a curling free kick just beyond the top corner in the 51st minute, his shot brushing the side netting on its way wide.
But Watford doubled their advantage five minutes later, Deeney feeding Anya who in turn picked out Guedioura for a simple close-range finish.
O'Brien should have pulled a goal back when he wrestled his way past Tommie Hoban to leave him with a clean run on goal but the youngster was denied by Gomes from a tight angle.
Two of Harris' subs combined when Gregory flicked on Martin's cross for Maierhofer, but Gomes came charging off his line to prevent the Austrian forward from heading in the loose ball.
Martin then picked out Gueye at the far post but the Frenchman's first-time drive bounced into the ground and harmlessly over the bar.
Gueye was able to test Gomes from Maierhofer's knock-down in the 81st minute but the Watford keeper made a comfortable save at his near post.
With Millwall becoming increasingly desperate, the visitors grew more dangerous on the break and Forde did well to thwart Odion Ighalo, Almen Abdi and Deeney late on.