I think it depends on whether Khan can handle Diaz's punch or not. I definitely don't give David much a chance, but he is tough as hell, and Khan didn't seem to sit down on his punches at all against Barrera, and I think Diaz even at this stage is more willing to take a punch to land a haymaker than Barrera was at the late stage in his career. Though it is more than likely Diaz gets circles boxed around him.