Ander Barrenextea and Brais Mendez struck the goals for La Real on Thursday night.
Imanol said afterwards: "Well, because we were right inside the areas, in the famous areas. Last day I think we played a much better game than today from area to area, but we lacked the quality where the difference is made. And today, without playing such a brilliant game, we were right in the small details.
"After Sunday, we insisted on getting the outside players and the second line players into the area and, although we didn't create as much, we did have that intention. The way the team pressed was different and the play that led to the second goal was an example."
Imanol has now led La Real into the Copa semifinals three times in the last six years.
He added, “I am very happy to be in the semi-finals once again. I would like to congratulate the players and the fans, who have helped us tremendously, especially when Osasuna were better in the first few minutes. I think that with time we will realise what it means. I am very sorry that I think there are some who are not enjoying this moment.”