Goals from Carl Asaba and substitute, Ben May handed the visitors a morale-boosting win in their own battle at the opposite end of the table, although they remain five points adrift in the bottom three following Sheffield Wednesday's equally impressive triumph at Wolverhampton Wanderers.
But the eventual outcome did not look on the cards during the opening half hour in which the Golden Boys pinned the Lions back for long periods and seemed set to make a breakthrough.
And the goal their approach play merited should have arrived after 25 minutes when Zak Whitbread was adjudged to have handled in the penalty area by referee Mr. A. D'Urso.
However, Gavin Mahon rather telegraphed his spot-kick and Andy Marshall saved it low to his right to the delight of the travelling South East London support massed behind him.
That let off boosted Millwall's confidence and as the rain began to teem down they perhaps should have taken the lead in the last minute of the first half when they broke three on one. Alan Dunne slipped in Asaba but the former Brentford striker shot wide of the target as he lost his footing on the increasingly greasy surface.
But the Lions began to look more likely to score after the break and it came as no real surprise when they took the lead after 66 minutes.
Jamie Vincent slipped in Colin Cameron from the left flank and the on-loan Wolves midfielder calmly rounded keeper Ben Foster before squaring the ball to gift Asaba his fourth goal of the season.
Not surprisingly the Golden Boys then began to press in increasing numbers as they sought an equaliser and they missed a good opportunity to do just that when Darius Henderson knocked a Lloyd Doyley cross back into the path of Alhassan Bangura but the substitute, who had only been on the pitch for barely a minute, shot wide of the near post.
It then took an outstanding Marshall save to prevent the home side getting back on level terms when he acrobatically tipped over an audacious curling shot from Ashley Young.
As
So a fifth home reversal of the season has left the Golden Boys with it all to do if they are to realise Aidy Bothroyd's ambition of automatic promotion. All is not lost though and this
For Millwall, a tremendously combative performance which should hold them in good stead for the remaining matches of the season.
The grim reaper has the relegation trap door primed, but with Brighton & Hove Albion at home next Saturday and trips to out of form Southampton on Easter Monday, and a last day of the season jaunt to bottom placed Crewe Alexandra still on the agenda, Tuttle's men may, on the evidence of this match, dramatically escape with their life.