Joao Felix would be "at a higher level" if he had joined Real Madrid instead of Atletico Madrid, claims Carlos Carvalhal.
Atletico shelled out €126 million (£122m/$142m) to sign Felix from Benfica ahead of Antoine Griezmann's departure for La Liga rivals Barcelona last year.
However, the 20-year-old has only contributed six goals and three assists in 28 appearances, with ankle and hamstring injuries sidelining him for separate short spells.
Carvalhal, who is the head coach at Primeira Liga side Rio Ave, does not think the style of football played under Diego Simeone suits Felix.
He believes a move to their arch-rivals Real Madrid would have put a fellow Portuguese in a better position to develop his game.
"Joao Felix 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 great level. But I'm not sure Atletico's way of playing is the best for him," Carvalhal said on Cadena SER.
"That was my doubt when he signed for them. Diego Simeone is a great coach, his teams are very strong, very competitive, but Joao Felix does not seem to be the perfect player to be there.