Millwall were blown away by a four-goal first-half salvo from high-flying Carlisle.
The home side took the lead after 15 minutes when Joe Garner headed home a Marc Bridge-Wilkinson freekick.
The Lions nearly levelled on 24 minutes when Dave Brammer's curling effort with the outside of his right foot hit the post, but almost immediately Carlisle increased their lead when Danny Graham escaped the Millwall central defenders and his soft shot wrong-footed Rab Douglas.
Graham added a third from David Raven's 33rd minute cross to effectively put the game beyond Millwall's reach. But worse was to follow when Richard Shaw was stretchered off with concussion after being caught by Garner who was booked.
Bridge-Wilkinson conjured a magical fourth from a freekick which beat Douglas all ends up, sending Millwall into the break desperately looking for a way back.
Home keeper Kieran Westwood was forced into a flying save within seconds of the restart, denying Gary Alexander a great ball in from Ali Fuseini.
And Westwood produced a stunning double save to deny Neil Harris and Alexander in quick succession as The Lions tried in vain to claw their way back into the match.
Skipper Paul Robinson was also thwarted by Westwood, who somehow tipped the defender's bullet header over the bar after 70 minutes.
Alan Dunne twice saw close-range headers flash wide as Millwall tried desperately to reduce the arrears.
But sadly The Lions could not muster a consolation goal or two that their second-half effort deserved.

Carlisle United: Westwood, Raven, Aranalde, Bridge-Wilkinson, Livesey, Murphy (Arnison, 61mins), Lumsden, Graham, Garner (Gall, 46mins), Hackney, Anyinsah (Carlton, 78mins).
Subs not used: Smith, Howarth.
Scorers: Garner (15mins), Graham (29, 34mins), Bridge-Wilkinson (45mins).

Millwall: Douglas, Senda, Frampton, Robinson, Shaw (Bakayogo 37), Dunne, Brammer, Alexander, Harris, O'Hara (Fuseini 34), Simpson.
Subs not used: Day, Hackett, Barron.

Referee: G. Laws