Say if you are bad at doing your job, you made mistakes and caused the company going backwards and lost a great deal of money due to your ineptness. Have some diginity and resign.
So Martinez should have just said "I'm resigning, don't worry about that £10m (or whatever it was) I'm entitled to that is in my contract"
I don't care who you are, or what job you do, or how much you cock - up in that job, no one in their right mind is going to do that.