Millwall suffered a defeat at The Den on Wednesday afternoon as Middlesbrough were 2-0 winners in the Sky Bet Championship.
Britt Assombalonga scored a highly controversial goal to give the visitors the lead in the second-half, before Ashley Fletcher netted the second from the penalty spot after he was brought down by Jake Cooper with just minutes remaining.
Lions boss Gary Rowett made two changes from Friday night's win over Charlton Athletic, with Shaun Williams and Ben Thompson coming into the starting XI at the expense of Jayson Molumby and Ryan Leonard, who both dropped to the bench.
The opening stages saw the ball travel to both ends of the pitch at speed, but neither goalkeeper was troubled. With nine minutes on the clock, however, a Marvin Johnson cross fizzed across Millwall's goalmouth, but there was no touch and the ball rolled to safety.
Thompson, back in the side, then a shot deflected behind by George Friend four minutes later, before Matt Smith headed over the crossbar from the resulting corner-kick, taken by Williams.
Neil Warnock's side ventured forward as the halfway point of the half approached, firstly through Ashley Fletcher's header from a Johnson free-kick and then as Paddy McNair sent two dangerous crosses into the penalty area, but the biggest talking point came with 23 minutes on the clock as Djed Spence tumbled under the close attentions of Murray Wallace - referee Tim Robinson was unmoved.
Mahlon Romeo's cross looked for Thompson after some neat football just before the half-hour mark, but the midfielder's attempted volley was blocked behind by Ryan Shotton. At the other end, Boro - who were perhaps having the better of the half to date - sent another teasing ball into the box through Djed Spence, but fortunately for The Lions, there was no touch to divert it into the net.
Ten minutes from the break, Bartosz Bialkowski had to be on guard to acrobatically tip McNair's shot over the crossbar, before an effort on the turn from Dael Fry gave the stopper less problems, rolling wide. Jed Wallace's curler then nestled in the arms of Dejan Stojanovic as the half came to a close.
Mere seconds into the second-half, Middlesbrough could - and perhaps should - have taken the lead, but after Johnson cut the ball back to the unmarked McNair, he sent his effort over the bar. Ex-Millwall man George Saville was then about to pull the trigger inside the penalty area, but an expert tackle from Ryan Woods prevented the midfielder from striking.
Shaun Hutchinson's cross was nodded by Matt Smith with 56 minutes played and sliced into the air by Jonny Howson, but the ball landed on the roof of Stojanovic's net and went behind for a corner - one with Cooper nodded wide from.
A triple substitution just past the hour-mark saw The Lions revert to a 4-4-2 formation as Tom Bradshaw partnered Smith, and it almost paid dividends as Connor Mahoney's cross was headed goalwards by the big man, however Stojanovic extended his hand to pull off a magnificent save and keep Boro's sheet clean.
The changes had breathed new life into The Lions, and Stojanovic was again to the rescue for the visitors as he stopped Mahoney's drive with his feet, but with 68 minutes on the clock, Middlesbrough took the lead in highly controversial circumstances.
Cooper looked to have been fouled on the far side of the pitch, but, incredibly, no decision from referee Robinson or his assistant meant Assombalonga and Fletcher were in a two-on-one situation with Hutchinson - the latter squared to the former, who had no problems in slotting the ball past Bialkowski.
Jed Wallace then fired wide after latching on to Bradshaw's takedown, before the two reversed roles with 10 minutes remaining, however Bradshaw sent the ball well wide from Jed's free-kick.
Mahoney's through ball then sent Jed Wallace inside the box but his cross was blocked, but at the other end, Fletcher beat the offside trap with four minutes remaining before being brought down by Cooper, with referee Robinson signalling for a penalty. Fletcher stepped up to score and double Boro's lead.
A duo of corners were forced in stoppage-time as The Lions looked for a consolation, but they were to no avail.
Millwall: Bialkowski, M. Wallace (Ferguson 83'), Hutchinson, Cooper, Williams (Molumby 63'), J. Wallace, Thompson (Bradshaw 63'), Smith, Romeo (Mitchell 83'), Pearce (Mahoney 63'), Woods. Subs not used: Steele, Leonard, Skalak, Burey.
Middlesbrough: Stojanovic, Friend, Shotton, Fry, Assombalonga (Tavernier 76'), Fletcher, Howson, McNair (Clayton 82'), Johnson, Saville, Spence (Dijksteel 83'). Subs not used: Pears, Moukoudi, Roberts, Nmecha, Wing, Coulson.
Scorer: Assombalonga 68', Fletcher pen 87'
Booking: Assombalonga, Saville, Howson
Referee: Tim Robinson