The midfielder will join Villa in a Bosman transfer at the end of next month.
Longoria told RMC: "Kamara? Individual choices must be respected. I've always said that you have to respect the player's decision. We talked a lot with his entourage by offering different possibilities.
"But we must remember one thing that in the current world of football, more and more players trained at the club leave free. This is a subject of discussion between European leaders. This is an increasingly dangerous trend.
"Kamara was very invested in the project this season. His level of commitment was decisive in achieving our objectives.
"I don't like talking about individual discussions. In life I believe in the word. There were a lot of words given that were not respected."
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