Former Manchester City defender Sylvain Distin questioned Pep Guardiola's treatment of John Stones.
Stones grew to enjoy his role at the heart of Martinez's Everton squad but was criticised for the mistakes he made.
Guardiola has defended the centre-back during his time at the Etihad.
But Distin worries that the mentality set from two similar managers may mean Stones fails to improve as a defender under Guardiola.
"I know he reacted well every time but I’m a bit scared that because of the last two managers he has had that put him in that pattern of 'it’s okay to make a mistake don’t worry," he told The Beautiful Game podcast.
"With the team and manager they have now he is the perfect player. No disrespect to him, he is a top manager, but will Guardiola make him a better defender? I can’t see it.
"He will make him a better player coming out from the back with the ball but better defender? I don’t see it happening."
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