Lopetegui didn't last the first-half of the season before being dumped.
Kroos said on his podcast: "Lopetegui's dismissal was the one that hurt me the most personally because he is a first-rate coach and person.
"He just had a sh***y moment when he became a coach here. I was very happy for him when he won the Europa League with Sevilla, he deserved it.
"I think he did a great job but he was unlucky and if you don't have results it is not good for the club."