Silva does have a bit of a puncher's chance but very small. I'm not even sure if Silva could knock him out with a full force punch to the jaw, may have to get a couple in a row. A prime Silva vs. a raw Jones could probably beat him, but I don't think there is any more than a small possibility that Silva could beat him now.
Silva in his prime vs. a natural weight class Jones I'm not so sure of though. And by natural weight class I mean either Silva as his natural weight at LHW or Jones at MW.