United have upped their bid for the pair to £38 million.
Martinez said: "The way you work in the transfer market is to always think about the unthinkable. You always have to work in a way which means that if the worst was to happen, and you picked up one or two injuries, you need to replace players.
"That's the norm so you always have to work like that.
"I have told the chairman (Bill Kenwright) I don't want to know anything that's going on (with United). I only want to know the final news. I have had enough of 'he said this, he said that'.
"This is sensitive."
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