Maidana. Diaz belongs nowhere near the 140 division. Let's remember, Malignaggi hurt Diaz atsch Maidana would brutally KO the man.
Diaz would survive at most for 7 rounds. Some guys you just shouldn't trade with, Diaz never had the boxing mentality, he's a warrior through and through and he's got decent whiskers (regardless of what anybody says about Paulie hurting him) but Maidana would break him down piece by piece. I think he'd get the job done faster than Marquez, considering he's less of a counter puncher and would just meet him head on, and win. He wouldn't bother boxing Diaz, he could, but it'd be pointless.
Yeah but to get rocked by Malignaggi would mean a decent punch from Maidana might decapitate you. I agree with dude above, Diaz does not belong in 140.
Juan Diaz has never been an elusive target, he operates most effectively at coming forward and throwing punches in bunches. What would this achieve against Marcos Maidana? Absolutely nothing. Diaz doesn't carry enough pop to to hurt Maidana or deter him, and Diaz has been wobbled and stopped by lesser punchers. I can only see this ending in devastating fashion, and Maidana would have his hands raised.
Diaz' prime was never at 140, and Maidana has never fought at 135. So, the fight would have to be at 140...where Diaz wasn't in his prime nor was that his weight class. Anyway, I would take Maidana by stoppage.