Millwall captain Danny Shittu headed his side into an FA Cup semi-final against Wigan as Blackburn's season took another dismal turn at Ewood Park.
Shittu, whose only other goal this season came in the Lions' fourth-round triumph over Aston Villa, came close to scoring with a pair of spectacular long-range efforts when the first attempt to settle this all-Championship quarter-final finished goalless at the weekend.
A thumping header more akin to a robust centre-half was Shittu's chosen method on this occasion as he converted Chris Taylor's 43rd minute corner and settled the contest.
As at the weekend, Blackburn sorely lacked creativity and #11million strike force Jordan Rhodes and Leon Best drew a blank once more, although the latter had a second-half shot superbly cleared off the line by Shane Lowry.
Millwall now face a rematch of their 1999 Wembley defeat to Wigan in the Football League Trophy final, while results on Saturday could send Rovers into Sunday's east Lancashire derby against Burnley just three points above the relegation zone - an unthinkable second-consecutive relegation hovering ominously into view.
Injuries sustained by Adam Henley and David Bentley during Sunday's bruising goalless encounter at The Den brought fit-again duo Martin Olsson and David Dunn into the Rovers' starting line-up - the latter making a first start since October - while Millwall were unchanged.
Blackburn started brightly and, having failed to register a shot on target at the weekend, they tested Lions goalkeeper David Forde through Best's speculative fourth-minute drive.
The Republic of Ireland international had a left-footed effort deflected behind in the 15th minute and, from the resulting corner, club stalwarts Morten Gamst Pedersen and Dunn combined for the latter to arch a shoot past the far post from 18 yards.
Moments later Millwall attacked and Danny N'Guessan felt he was impeded in the area by Rovers skipper Scott Dann when trying to reach Andy Keogh's cross, but referee Mark Clattenburg disagreed.
In the 20th minute, Blackburn goalkeeper Jake Kean created danger all of his own making by leaving himself stranded en route to claiming a long Lowry free-kick that Rob Hulse glanced wide.
Millwall had grown into the contest and Chris Taylor flashed a 20-yard drive beyond the crossbar at the end of a jinking run.
Josh King fired over from range following a well-constructed Blackburn counter attack involving Leon Best and Jason Lowe, but at telling spell of Millwall pressure arrived before half-time.
N'Guessan twice had shots blocked by Lowe as Rovers failed to clear a corner before Taylor's deflected shot crashed into the side netting.
The former Oldham midfielder delivered the next set-piece and Shittu was allowed room to power home from close range.
Blackburn manager Michael Appleton signalled attacking intent by replacing Markus Olsson with former Portugal international striker Nuno Gomes at the break, Martin Olsson reverting from the left-wing to his more familiar position of left-back.
Lowry produced a telling block when King volleyed goalwards after Dann headed Pedersen's 49th minute corner across goal.
Keogh was the second player into Clattenburg's notebook - Shittu elected to celebrate his goal bare-chested - for a foul on Olsson after the hour but Pedersen wasted a promising free-kick position as frustrations among the home faithful audibly grew.
But Best brought them to their feet in the 63rd minute, drifting through a static Millwall backline to see the sliding Lowry clear his from the goalmouth.
A sustained period of Blackburn pressure followed, Lions boss Kenny Jackett responding by sending on Nadjim Abdou for N'Guessan and switching his 4-3-3 formation to a more conservative 4-5-1.
It proved enough to thwart Rovers, whose challenge faded badly.
Mark Beevers blocked a Nuno Gomes strike in the final minute before Taylor blazed wastefully over when trying to add late gloss to the scoreline.