I wouldn't give up my belt if i was Brook, i don't think he can hold his own with the elite in the Middleweight division.
I think an on for Saunders boxes his head off, Jacobs beats the shit out of him too and even Eubank Jnr would beat him.
I reckon he knows it too which is why i think he'll fight Spence and defend his title - time will tell
I think Spence v Brook is a seriously brutal fight so hope it happens.