A late Kari Arnason header condemned Millwall to defeat in a relegation six-pointer at fellow strugglers Rotherham United.
Martyn Woolford had fired The Lions into a deserved 19th-minute lead, but seconds after the break Danny Ward's shot took a massive deflection off Jos Hooiveld to haul The Millers level and Arnason completed the turnaround with a heartbreaking late winner for the Yorkshire club.
Millwall manager Ian Holloway stuck with the same XI that started against Sheffield Wednesday in midweek, with Woolford and Gary Taylor-Fletcher both passing late fitness tests having sustained a rib and foot injury respectively in that match.
The Lions looked lively in the opening exchanges with long forward balls from Woolford, twice, and skipper Alan Dunne inches away from finding the marauding Lee Gregory up front.
Rotherham responded and it took some expert defending from Jimmy Abdou and Alan Dunne to help avert the danger to clear two corners from Ben Pringle.
Keeper David Forde then flung himself across goal to push away a curling 18-yard free-kick from Pringle, but it was Millwall who made the all-important breakthrough after 19 minutes.
Shaun Williams dinked in an angled ball into th danger zone, Taylor-Fletcher nodded the ball into the path of Woolford who despatched a crisp finish beyond the reach of Adam Collin in the home goal.
The Lions had a great opportunity to double their tslly after 37 minutes when the impressive Taylor-Fletcher slipped the ball through to Gregory, but keeper Collin spread himself well to block.
Back came The Millers with Matt Derbyshire first charging down Forde's clearance and the ball spun over the bar and then glancing a header from Jack Hunt's deep cross narrowly wide of the upright.
However Millwall dug in and defended their precious lead so well in what had all the makings of a textbook 'smash and grab' raid.
Unfortunately the script didn't quite go according to plan and within 90 seconds of the second-half, Rotherham had hauled themselves level.
Derbyshire was the provider, teeing up team-mate Ward whose shot on the turn took a deflection off the unfortunate Hooiveld and beyond the reach of Forde.
Woolford was a whisker away from restoring Millwall's advantage on 52 minutes with a firm header that was hacked off the line first by Kirk Broadfoot and then Paul Green.
However The Lions were forced to make a change moments later when Taylor-Fletcher - who had already three times been forced off the field to receive treatment to a bloody head wound - was replaced by Ricardo Fuller.
The loss of Taylor-Fletcher was a massive blow and The Lions struggled to really get their attacking game going thereafter.
Rotherham nearly edged ahead on the hour-mark when Hunt's sizzling drive smacked the foot of the post, the ball fell invitingly for Green whose follow-up shot was superbly tipped over by Forde.
There was little between the two teams as the game entered the final 10 minutes but then up popped Arnason to meet Pringle's corner kick and head home the winning goal.
Try as they could to raise a head of steam for a final push for an equaliser, The Lions could not muster any further efforts on goal leaving Holloway's men six points adrift of safety and with a trip to promotion-chasing Middlesbrough on Tuesday night.
Collin, Hunt, Arnason, Broadfoot, Fryers, Newton (Hammill, 69mins), Green, Smallwood, Pringle, Ward (Frecklington 90+3mins), Derbyshire (Sammon, 89mins). Subs not used: Loach, Richardson, Milsom, Clarke-Harris.
Ward (47mins), Arnason (85mins)
Forde, Abdou, Harding, Dunne, Hooiveld, Williams, Tonge, Woolford, Fabbrini (Upson, 86mins), Taylor-Fletcher (Fuller, 58mins), Gregory (O'Brien, 66mins). Subs not used: King, Beevers, Nelson, Martinez.
Ref: G. Sutton
Att: 10,329 (away 1,309)