Aiden O'Brien scored his fourth goal of the season as Millwall stunned play-off chasing Brentford with a 1-0 victory to go within two points of the Championship's top six.
The Bees began the afternoon third in the Championship table, eight points behind Leeds, but could not cope with Millwall's fast start as they went behind inside eight minutes.
After Murray Wallace's goal was ruled offside, Jayson Molumby harassed goalkeeper David Raya into a mistake before O'Brien slotted home into an empty net.
The Lions' fine run of form has got them dreaming of the play-offs as well since Gary Rowett took charge, and they twice went close to doubling their lead during a frenetic start at The Den.
More high pressing saw the ball break to the in-form Jed Wallace, who lashed a volley over the bar, before Shaun Williams' long-range drive drew a fingertip save from Raya.
Brentford eventually began to show signs of promise and registered their first shot of the game after half an hour when Bryan Mbeumo's left-footed effort forced Bartosz Bialkowski into his first save of the game.
The visitors threatened again as half-time approached, following some combination play down the left side, Rico Henry saw a deflected effort easily gathered by Bialkowski.
Brentford eventually produced some bright moments, with the Millwall defence put on high alert when Ollie Watkins' inviting cross from the byline came zipping across the Lions' goal.
And as the game entered a minute of added time, scuffles broke out when referee Robert Jones booked Said Benrahma for kicking the ball into Jake Cooper after the whistle had already been blown.
Millwall began the second half much like they did the first, as Jed Wallace and Mahlon Romeo went close, but were forced to cling onto their lead following the restart.
Mbeumo's header from Watkins' cross was thwarted by Murray Wallace before Bees skipper Pontus Jansson headed over the bar from Josh Dasilva's corner.
Clear-cut chances were at a premium in the cross-London clash and Brentford were left ruing the one substitute Jan Zamburek had near the end when he shot wide at close-range.
As Brentford piled bodies forward, Millwall dug deep and had to survive four minutes of added time to seal their first league win at home in three attempts.
For Brentford, the narrow defeat sees them lose now fail to win on their past four trips away from Griffin Park.
