Heitinga could be allowed to leave in search of more regular first-team football.
Martinez told evertontv: "Johnny Heitinga is an issue we need [to resolve].
"I've been very open from the beginning that we had a conversation with Johnny and he will be allowed to try to play football and play minutes, and it's a bit unfair if he cannot do that with us.
"We need to find a solution and a respectful solution, because Johnny's been really influential in the level the team has achieved in his daily standards and the work he's put in on the training ground.
"If we can find an option where Johnny can play football that helps him get into the World Cup squad, that will be a fitting moment of his illustrious career.
"So that's the situation and we're going to find out [what happens] over the next 48 hours."
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