Felix left Benfica last summer to join Atletico in a €120m deal.
Carvahal told Cadena SER: "João Félix is a great player and I don't want to create controversy with my statements. He is a player with incredible technical ability, with a high level.
"But I'm not sure if Atlético de Madrid's way of playing is the best for him. That was my doubt when he signed for the Rojiblanco club. Diego Simeone is a great coach. Their teams are very strong, very competitive. But João Félix does not seem the perfect player to be there."
He continued: “In a different context we would see a great Joao Félix. It will be a little difficult and it will take more time. You are going to have to transform as a player.
"If he went to a team like Real Madrid he would be at a higher level. The context would be more favourable for him. This is not a criticism of Simeone, there is no doubt what he has achieved. His work speaks for him. I just think that this marriage is not the best."