A bizarre own goal by Esteban Cambiasso saw West Brom leave the King Power Stadium with all three points in Saturday's Premier League clash.
That win came on the back of West Brom's 2-1 defeat to Bournemouth on Tuesday, a match in which Irvine received some criticism for making 10 changes from the team that drew 2-2 with Crystal Palace.
Head coach Irvine, though, believes that his decision prevented his side from becoming fatigued.
"I'm not satisfied with what happened on Tuesday night, I'm still hurting about that," Irvine said.
"But the fact is if we had played the same team and gone down to Bournemouth, perhaps gone to extra-time, we would have been risking problems at the end of the game against Leicester.
"Every time I turned round [Leicester manager] Nigel [Pearson] was putting on another forward and clearly we were going to be put under pressure if we were ahead.
"We needed players who were physically and mentally ready to cope with that and I thought they did really well."
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