Just five years earlier, he had combined a nine-to-five life as a joiner on just £70 per week with playing semi-pro football for minnows Coagh United in his native Northern Ireland.
At 24, Dallas felt the move to Leeds United – and a reunion with Uwe Rosler, the manager who had brought him to England – would continue that rapid rise.
The reality, however, proved rather different with Rosler being sacked just a couple of months later as United then rather lost their way under a succession of appointments that promised much more than was ever delivered.
Garry Monk and Thomas Christiansen made encouraging starts in the post but only now, under his sixth manager, does Dallas seem to be part of a United side genuinely capable of sustaining a challenge for the Premier League.
“It is hard really to pinpoint,” said the Northern Ireland international when asked what had most changed for the better under Marcelo Bielsa. “But I do think he has just got everyone reading off the same sheet.
“Everyone is working hard and we keep coming back to fitness, which is a big part of it.
“The way he has got us playing football, everyone believes and he shows confidence in every player.
“You have got to believe in the players around you and certainly this manager has come in and got the best out of us. We can only take it one game at a time and you are only as good as your last game. We have just got to keep pushing forward.”
Dallas will today come up against the club who brought him across the Irish Sea in 2012 after spotting his potential at Crusaders.
His three years in London would prove to be among the most eventful in Brentford’s history.
The tone was set on the final day of his first season, as the Bees and Doncaster Rovers went head-to-head for the prize of promotion from League One.
Brentford being awarded a 94th-minute penalty with the score goalless suggested the visitors from Yorkshire would be heading for the play-offs but Marcello Trotta fired against the crossbar.
Play immediately raced up the other end, James Coppinger scored the most dramatic of winners and Rovers went up as champions.
After such a momentous body blow, Rosler’s side losing at Wembley in the play-offs to Yeovil Town came as no surprise but redemption came a year later via a second-placed finish behind champions Wolverhampton Wanderers.
Dallas featured heavily during the run-in and again the following season in the Championship as Brentford finished fifth. Defeat to Boro over two legs was then Rosler’s signal to return to his former club and bring the wideman north to Leeds.
Three years on and there is a growing belief that this could finally be the season when United’s long wait for a return to the top flight could come to an end. Such expectation sits comfortably with Dallas.
“If you play for Leeds you know the expectations of the crowd,” he added. “And the pressure that comes with it.
“There is no denying we are at a massive club and you have got to have big shoulders. You have got to take criticism when it comes your way.
“It works the other way if you get praise as well so it comes with the club.
“As the season goes on I hope there is more pressure because it means we are doing something good.”
United head into the lunchtime clash with Dean Smith’s men knowing victory should, barring a huge win later in the day for Middlesbrough or Sheffield United, be enough to guarantee top spot during the season’s second international break. It won’t, though, be easy with the club Dallas left behind in 2015 sitting sixth in the table.
“Brentford are one of the best footballing sides in the league,” said the wideman, who in two of the past three seasons has finished below Brentford in the table. “We are going to be in a tough game.
“They thrive on coming to big stadiums and atmospheres. Since coming up, Brentford have always been there or thereabouts. They have a great manager and a striker (Neal Maupay) bang in form. If we are not on form, we could be in for a tough afternoon.”
Dallas, who had to spend a month on the sidelines earlier this season through injury, is expected to make his first start under Bielsa today in place of the injured Barry Douglas.
As one of the more long-serving members of the Elland Road squad, he is in a good position to judge how things have changed under the Argentinian.
“We have always been fit,” he said. “I think, as a professional athlete, you have to be. But he has come in and the fitness side of things has been different from what we had done before.
“The way we have gone about our aerobic running and high intensity running, I think if you look at our stats throughout the games we have played – our running is through the roof.
“We are fitter, we are stronger, we are leaner and we keep going right until the final whistle.
“It is statistically shown that if you overrun teams you will have the majority of the ball and most of the time it comes out with a positive result.
“We have just got to keep working hard, it will all be worth it,” he added.