Do you understand the difference in speed and athleticism here though? I'm not sure you do, Floyd would jab her into a living death as the great scholar Ken Shamrock would say. Rousey definitely has a small chance to win, but it is a small one.
Edit:
I do get the incredible difference, but that's not the point (and that point was also missed with the Lucia Rijker video). Let me give an example that's easier to quantify than boxing vs MMA.
Usain Bolt is the greatest sprint athlete of the past decade, if not ever. Marianne Vos is the greatest female cyclist of this generation. There is no doubt who is (by far) the greatest athlete. Heck, in absolute terms, Marianne Vos isn't even up there with the 1.000.000th best male sprinting athlete.
Now, if we assume that Bolt cannot ride a bike and will rely solely on his running, who will win a top speed competition, bikes allowed? Truth is that Vos will easily outpace a running Bolt with her bike, not because she is such a good athlete (at least not in comparison to your avarage male athlete, let alone Usain Bolt) but because the used medium, cycling, is greatly superior to running - speed wise.
In the case with Rousey vs Floyd, the idea that he will surely connect in a decisive way before they clinch is simply not realistisc. Floyd is not conditioned to avoid a clinch at all costst. I honestly think that even the average amateur boxer (male of female) can get into a single clinch with Floyd before they get knocked the fuck out, simply because it's really unavoidable. Yeah, Floyd has great footwork, but that's developed with the idea of a boxing opponent; someone that stands in front of him at a certain range, not with the idea of avoiding clinches from bull rushing opponents or opponents that dive at your legs.