Former Tiger Martyn Waghorn scored a goal in each half to secure the points for the Rams as the Tigers fell seven points behind their opponents in the play-off race.
It might have been different had Kamil Grosicki not missed a great early chance prior to Waghorn putting Derby ahead, while Irvine himself sent a header agonisingly wide before the Rams striker’s second of the afternoon sealed victory for the hosts.
Reflecting on the defeat at Pride Park, Irvine said: “Obviously everyone was extremely disappointed after the game.
“I don’t think we were at our free-flowing best, particularly in the attacking third, but it wasn’t a poor performance.
“We still created three or four clear-cut opportunities and with the quality we have going forward, we can still do that even when our general play isn’t quite clicking as we know it can.
“It was just frustrating that we couldn’t capitalise on those chances and, ultimately, that was the difference between the two sides on the day.
“We conceded the first goal at such a horrible time in the game, just before half-time.
“But, we regrouped during the break and I thought we came out after the restart and looked decent.
“I flashed a header across goal and we had a few other little moments but we were then the architects of our own downfall, losing the ball in our own corner and allowing an unmarked man a free shot from six yards.
“It’s all about key moments in games at this level and they were very clinical with their clear-cut chances.”
Irvine and his team-mates will have the chance to put the defeat behind them when they host Rotherham United at the KCOM Stadium on Tuesday night, with the Australian international eager to see Nigel Adkins’ side produce an immediate response against the Millers.
“Saturday was an opportunity lost to close the gap on the play-off spots but we’ll refocus and go again,” he added.
“We’ve just got to keep going, stay in touching distance and wait for our opportunities. As long as you’re in touching distance, there’s always a chance.
“We’ve shown we can string a run of results together and that’s what we’ll look to do once again.
“The most important thing now is our recovery and getting ready to play an extremely important game against Rotherham United at the KCOM Stadium on Tuesday night.
“Three points in that game keeps us right in the mix and that will be our only aim. Our home form has been excellent of late and it’s vital that we continue that.”