BetUS has granted my previous request and posted odds on each team to go undefeated during the 2008 NFL regular season. Using the winning percentages derived from each team's over/under, I've determined the actual odds of each team going undefeated for comparison. The list is quite long, so I've only posted the odds for the five most likely teams below, but the odds for each team are here.
If you believe the over/unders--and it would be silly not to--then the Patriots are by far the best bet of the 30 teams. That's not to say they're a good bet; not even close. As you can see above, they're expected to go undefeated about 1.3% of the time, while it needs to happen at least 6.3% of the time for it to be a good bet. But compared to the rest of these, it's a bargain.
The reason for this is that the relation between W% and undefeated percentage is not linear. A .700 team does not have twice as good a chance of going undefeated as a .350 team; they are actually about 65,000 times more likely. This is quite easy to see if you do the simple calculation (.700^16), but most people obviously do not. So as you go down the list of teams, the chances of them going undefeated decrease dramatically, while the odds change only slightly.
Which brings us to what may be the single worst prop I've ever seen:
They've also posted more detailed odds on the Pats, regarding their exact regular season record. Again, I'm using the .761 W% derived from their over/under odds, to come up with the "true" odds of each record:
I have no idea how they came up with these.
The Pats' over/under is 12.5. I think it would logically follow that their two most likely win totals are 12 and 13. Yet BetUS has installed 15 as the favorite, closely followed by 14. This makes no sense.
Maybe the thinking is that they went 16-0 last year, but that was obviously somewhat fluky, so this year they'll go 15-1? I honestly have no idea.
This has the effect of putting value in each number between 9 and 13. That is pretty amazing, since all of these add up to 124%. The best bet here is 10-6; it's not often that you can get 15-1 odds on something that happens nearly 10% of the time.