United’s Elland Road encounter with mid-table visitors Brentford looked destined to end goalless only for Kyle Bartley to head home an 89th-minute winner from an inviting cross from Dallas.
Brentford’s Scott Hogan incorrectly saw his first-half effort from close range ruled offside and while Leeds upped their game after the interval, Dallas conceded that Garry Monk’s men were some way short of their best.
Dallas also echoed Monk’s sentiment’s that “winners win” after setting up a dramatic decisive goal that elevated Leeds from sixth to fifth.
United have picked up 34 points from their last possible 48 – the third best record in the division over the last 16 games – with them having also won seven of their last nine league fixtures at Elland Road.
Saturday’s success also made it quickfire back-to-back victories for Leeds, with last Friday’s disappointing 2-0 loss at Brighton having been followed by Tuesday evening’s 2-0 defeat of third-placed Reading.
“It’s a sign of a good side that we can win ugly as they say,” said Dallas, reflecting on Saturday’s victory.
“We have shown that and I think everybody knows it wasn’t our best performance this season. But you get the same amount of points for winning ugly as you do for winning nice.
“Back-to-back victories in this league is massive. The gaffer touched on it with us before the game that it’s vital in this league .
“We have shown that we are able to bounce back from a defeat like we did last week and to do something in this league you have got to build on that. We have done that.”
Brentford shaded a pretty dull first half at Elland Road with the pacy Hogan looking dangerous and seeing a diving header saved by Rob Green before his 42nd-minute effort from close range was incorrectly ruled offside.
Nico Yennaris also saw a low shot deflected just wide and Romaine Sawyers wastefully missed the target when well-placed just before the break.
A United side missing top scorer Chris Wood with a hamstring injury saw their best chance of the first half fall to Kemar Roofe, whose effort was deflected just wide, also shortly before the interval.
Brentford began the second half on the front foot and John Egan put a free header wide 10 minutes after the restart, shortly after Hogan went tumbling down in the penalty area amidst half-hearted appeals for a penalty.
Leeds finally found some sort of form in the last half-hour and right-back Luke Ayling squandered two fine chances to score when blazing over and then wide from inside the Brentford area.
In between, Souleymane Doukara fluffed the best chance of the game when a majestic pass from Dallas released the striker one on one with goalkeeper Daniel Bentley at an angle but Doukara prodded a low effort just wide of the right-hand post.
A goalless draw looked inevitable but after determined work from Hadi Sacko bagged Leeds an 89th-minute corner, Sacko and Dallas combined before the latter delivered a fine cross from the right to Bartley, who towered above the Brentford defence to power home an unstoppable header.
Brentford were then given four minutes of stoppage-time to save themselves and almost netted an equaliser when Egan’s overhead kick clipped the crossbar before bobbling over.
Leeds had done enough to bag yet another home victory with Bartley’s late intervention preventing United from slipping out of the play-offs after Sheffield Wednesday stayed within one point of them by bagging an even later winner in a 1-0 success at home to bottom club Rotherham United.
Derby County, instead, dropped out of the top six after drawing 2-2 at Fulham.
Leeds will return to action at 11th-placed Preston North End on Boxing Day, when a victory could take them third.
“We are pushing and we are in the play-offs but we can’t look too far ahead of ourselves,” said Dallas.
“We have got to just take it one game at a time and that’s Preston on Boxing Day.”
United head coach Garry Monk beamed: “We’ve won seven of our last nine home games and that’s great.
“But it was obvious we weren’t at our best. I thought we looked tired, especially in the first 60 minutes. The one thing this team has – we try to instil it in them – is that belief to fight every second they’re on the pitch.
“The sense was that it was going to be one of those days but it was a great header from Barts and I think the roof came off the place when that goal went in.
“It’s great to see that mentality, fight and spirit from the players to keep going right to the end. Winners win.”