MIDDLESBROUGH saw their slender play-off hopes effectively come to an end at the Riverside Stadium this afternoon – despite a brilliant free-kick from Emmanuel Ledesma.
Two goals from Austrian striker Stefan Maierhofer in the first half proved crucial at both ends of the table as Boro missed a golden opportunity to close the gap to the top six to four points.
Instead Aitor Karanka will now be leading his team to Reading on Tuesday knowing that a seven point gap with just three matches remaining appears too much of a tall order.
It was Karanka's decision to stay faithful to the wing-back system which served him well at promoted Burnley a weekend which backfired.
With Albert Adomah and Ledesma operating as the wide men both in an attacking and defensive sense, Millwall's Lee Martin capitalised down the left.
He was afforded too much space inside the opening half an hour and he put both goals on a plate for Maierhofer to nod in on 16 minutes and then half an hour before Karanka changed things.
The Lions, who have climbed out of the relegation zone, would have added to the lead had it not been for Dimi Konstantopoulos in the Middlesbrough goal.
The home fans did have something to cheer ten minutes from time when Ledesma, who had been poor down the left, curled in a precise free-kick from 20 yards after Danny Graham had been fouled.
A failure to find a second and then a third brought an end to Middlesbrough's four-match winning run and it also, surely, any lasting chance of sneaking in to the play-offs in the final few weeks.
MIDDLESBROUGH (3-1-4-1-1): Konstantopoulos; Omeruo, Woodgate Chalobah; Whitehead (Friend 85); Adomah, Butterfield (L Williams 60), Leadbitter (Main 73), Ledesma; Tomlin; Graham. Subs: Steele (gk), Varga, Hines, Morris.
MILLWALL (4-2-3-1): Forde; Edwards, Dunne, Beavers, Malone; Bailey, Williams (Morison 62); Martin, Garvan (McDonald 85), Woolford; Maierhofer (Abdou 73). Subs: Robinson, Easter, Jackson, Bywater (gk).