There are standard forms for players contracts copies of which are in display in Clifton Museum if anyone is interested.
But then it depends how the gaps are filled in as to what the player is entitled to.
So some players maybe entitled to guaranteed money, whereas others may not.
I'm sure the PFA monitors this very closely but in essence it depends what each individual contract says.

Richie Towell,s form dropped dramatically when he was on loan with us and his contract ran out with Brighton. PW openly admitted it was the reason we didn't try to sign him permanently