You really need 4 CBs to be reasonably safe, so even if Duffy features in Martinez's plans, if Heitinga goes, we need someone to come in.
Jagielka: Our captain who has been one of our most solid defenders for the past 5 years and has probably another 5/6 good years left in him.
Distin: He should have at least one good season left in him but it's about time Martinez planned for the future of the Everton defence.
Duffy: I think he could feature more under Martinez, he has shown in the past he can handle the Premier League and he has been making noises about wanting to play more for Everton. Could be a crucial season for him coming up.
Alcaraz: I expect this largely depends on Heitinga's future here and I am not sure how soon Martinez will solve this issue, otherwise there is no doubt other clubs will be interest in signing Alcaraz on a free transfer. Even if we don't sign him under the circumstances then it's not the end of the world, we just need to find a younger defender with more potential and hope also Duffy can step up.