Burton had led 3-1 at half-time in the game, having been on top for much of the opening 45 minutes. However, Brentford found some rhythm in the second-half and scored four times to win the game and end Nigel Clough’s team’s six-game unbeaten run.
Irvine, Burton’s leading scorer this term with nine goals, said that he was disappointed with the way that the game ended, and stressed that the side cannot afford for a repeat performance before the end of the season.
"I'm sort of lost for words about it, to be honest. It's just so disappointing in every way,” said the Australian international.
"Our performances in the last few weeks have all been really positive and defensively, it has been our biggest strength, but we have let ourselves down with our second-half performance.
"I think there had to be an element of complacency, I suppose. Individual players can answer that question, but we didn't feel as if we came out with a different approach (in the second half). I think there might even have been an element of lethargy in the legs.
"We have put so much into the last few weeks and you can see the substitutes coming on and adding speed and things to the game, but I think we felt as the second half was going on going deeper and further back, and I don't know if maybe that played a part.
"I'm sort of lost for words about it, to be honest. It's just so disappointing in every way.
"Even saying that, we still had our opportunities and chances to go on and win the game or even take something at key moments in the second half and it is really difficult to put into words after an afternoon like that."
"The second half performance was way below our usual standard and hopefully it's a one-off.”
Irvine will now join up with his Australia teammates for the international break before the Brewers travel to Huddersfield on April 1st for their next Championship game.