Daniel Santos fought Margarito at 147lbs and 154lbs. And never got into the ring weighting 170lbs. That's the mexicans excuse.
Margarito made an effort to stay inside on Santos so he couldn't get full extention on his left. And as great as his chin is he was stunned for a couple seconds by a short left hook to the temple. I distinctly remember Williams looking bad in the second half of the Margarito fight after eating a couple hard straight rights. Had Tony kept that up Williams would have dropped. Santos is a bigger puncher than Tony when it comes to one punch power. Williams would not smother Santos because at 6'2 and 81 inch reach he'd be at a disadvantage anyways. His best bet would be to try and do to Santos what Dzinziruk did. Stay away as much as possible and use your height and reach to control Santos from a distance. The odds on Williams actually pulling that off are slim however, as Dzinziruk is a very capable boxer.
Admittedly I've seen more of Williams than I have of Santos, but I think the Punisher takes this by clear decision. It seems to me that Williams get underrated quite a bit here. I know he had that bad loss, but he avenged it by brutal KO and also owns a win over the hottest name in the welterweights right now.