Martial and Maguire aren't leaving unless they are replaced, if at all.
Maguire was club captain last year and is an England international, he doesn't fall into the dead wood category.
Nor does Martial really, who was in the 1st team squad. If we sign a striker, I assume he will leave if anyone wants him.
If we don't, he'll have to stay, and play.
Forgot about Telles, yeah he could do with leaving. Very much doubt we are paying his whole salary though, so some of his cost is covered at least.
As for Henderson, he's a different problem. His salary is irrelevant, his misplaced arrogance is not. He has to go, because he thinks he's good (he's not) so won't play second fiddle to anyone.
He can **** off for free, basically because he's a ****. Might as well get some fee in for him though.
