UFC 189 is widely viewed as The Conor McGregor Show, and the betting odds on his fight are supporting that. When McGregor was scheduled to take on Jose Aldo for the UFC featherweight title, the odds for that fight were very close. Since Chad Mendes has been brought in to take Aldo's place, it seems that the majority of betting folk are putting their money on the Irishman. Mendes opened as a -130 favorite, but that didn't last long at all. Here's how the line looks right now, via BestFightOdds:
For those new to BestFightOdds, they take the lines from many sports books and offer the best on each side in the handy chart above. If you'd like to see what each book is offering individually, you can do that over at their site.
What this means is that a ton of money has come in on McGregor, and the lines have been shifted as a result. Bookies want even betting on both sides so they're guaranteed a profit (with the built-in vig), so this doesn't really represent much in a true analysis of the fight, only where the money is going right now.
Personally, I use a few different betting sites and some of the prop bet prices are, frankly, incredible. Mendes winning inside the distance (ie. KO/TKO/DQ/Submission) is between +339 and +350 right now on the sites I checked. He is also anywhere from +325 to +400 to win via decision. McGregor is anywhere from even money to -140 to win inside the distance, and is as high as +650 to win a decision.
This is just a guess, but I think that the odds are going to go even more in McGregor's direction in the next couple of days as fight fans stream into Las Vegas, but the sharps will bet on Mendes late to bring it back around to where it is now. Again, that's just a guess. But I know I already have some money down on the fight, and will probably be putting some more on it depending on how the lines move.